Physics-Notes.doc

8/20/2019 Physics-Notes.doc

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INTRODUCTION TO PHYSICS.

DEFINITION OF PHYSICS

The science of the nature. Physics is that branch of science which treats of laws and properties ofmatter and force acting upon it. The department of natural science (Physics) which treats the causes

(Electricity, Head, Light, agnetism) that modifying the general properties of body! natural philosophy.OR Physics is an important branch of "cience which offers the study of matter and energy along with theinteraction between them.

BRANCHES OF PHYSICSThere are many branches of physics#1. Electronics$%t is the branch of Physics which deals with de&elopment of electrons, emitting the de&ices andutili'ation and controlling of electrons flow in electrical circuit designed for &arious purpose.$

2 Kinemetics$%t is the branch of Physics which deals with description of motion without reference to any opposingor e ternal force$.

. O!tics$%t is the branch of Physics which deals with light and its properties.

". D#n$mics$%t is the branch of Physics which deals with causes of motion and their effects$

%. C$lorimeter#$%t is the branch of Physics which deals with measurement of heat$.

&. Atomic !'#sics$%t is the branch of Physics which deals with properties and structure of tom$.

(. )ec'$nics$%t is the branch of Physics which deals with motion of particles or bodies under the action of gi&enforce$.

CONTRIBUTION OF )US*I)S SCIENTISTS1. IBNE+A*+HAITHA),-&%+1 - A.D/INTRODUCTIONHe was born in *asra a city of %ra+. He was one of the great uslim "cientist. He was a freat scholarof physics,mathematics,engineering,astronomy and medicine.CONTRIBUTION10He was a first man who discussed in detail about the luminous, non luminous and transparent

bodies.20 He also ga&e the structure and wor-ing of eyes.

0He ga&e us many laws of reflection and wrote many boo-s about the reflection of light."0 He also first time ga&e the idea that whene&er the ray of light is incident on an ob ect some of the incident rays are reflected from the ob ect and enter the eyes conse+uently the ob ect becomes&isible to the eyes which is accepted the scientific &iew.

2. A*+BERUNIINTRODUCTIONHe was born in *erun a small town of fghanistan.He wrote many boo-s on &arious sub ects li-e

physics,mathematics,culture,astronomy e.t.cCONTRIBUTION10 He discussed in detail about the mo&ement of sun moon and others planets .20He determined the densities of &arious metals .

0 He ga&e an idea that Earth is floating in the s-y li-e a ships in the water."0 He also awarded that he was a first who said that the &elocity of light is more than the &elocity ofsound.


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.)UHA))AD IBNE )USA KHA R )I

INTRODUCTIONbu bdullah uhammad %bn usa al 0hwari'mi was born in 23 .4 at 0hwari'm (0he&a), a town

south of ri&er 5 us in present 6'be-istan.

758T9%*6T%581, l 0hwari'mi was one of the greatest mathematicians e&er li&ed. He was the founder of se&eral branches and basic concepts of mathematics. He is also famous as an astronomer and geographer.20 He de&eloped in detail trigonometric tables containing the sine functions, which were latere trapolated to tangent functions.

0 l 0hwari'mi also de&eloped the calculus of two errors, which led him to the concept ofdifferentiation. He also refined the geometric representation of conic sections."0 l 0hwari'mi wrote a boo- on astronomical tables. "e&eral of his boo-s were translated into Latinin the early l/th century by delard of *ath and :erard of 7remona. The treatises on rithmetic,0itab al ;am


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of &ernier calipers or &ernier count ( 7). Least count of the &ernier calipers is calculated byL.7 alue of "mallest 4i&ision of ">Total 8umber of 4i&isions on "

)icrometer Scre? $64e screw gauge is an instrument that is used to measure thic-ness of a wire, glass, plastic and metal

sheets accurately up to 3.31mm. micrometer screw gauge has two scales, the main scale ( ") and

the circular scale (7"). The circular scale rotates o&er the main scale.

*e$st Co6nt ,*C/The smallest measurement that can be made with the help of a screw gauge is -nown as least count ofscrew gauge. Least count of the screw gauge is calculated by#L.7 Pitch of the "crew > Total number of di&isions of 7"where pitch is the distance between two consecuti&e threads of the linear screw.

P'#sic$l B$l$nce physical balance is an instrument that is used to find the mass of an ob ect. ctually, it is the le&er of

the first -ind with e+ual arms.

Sto! $tc' stop watch is an instrument that is used to measure accurately the time inter&al for any physical

e&ent. %t can be used to measure the fraction of a second.

)e$s6rin4 C#lin5er measuring cylinder is a glass cylinder of uniform area of cross section with a scale in cubic

centimeter or millimeter mar-ed on it. %t is used to measure the &olume of a li+uid.


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> J > J > K

> K > K

> K9 > K *

> K> K > K > K

> I

RESO*UTION OF A ECTOR $The process of splitting up of a signal &ector into two or more &ector is called the resolution of a&ector$OR

$The process of splitting up of a signal &ector into its components is called the resolution of a &ector$

RECTAN U*AR CO)PONENTS &ector which is not along a is or y a is it can be resol&ed into infinite number, but generally a

&ector can be resol&ed into its components at a right angle to each other

)ATHE)ATICA**Y PRO ED suppose a &ector D is denoted by a line * which ma-es an angle G with hori'ontal surface 5 . Droma point draw perpendicular to the hori'ontal surface 5 . > J > J

> K> K > K

> KD > K * Dy

> K> K

> K > G K *

5 > I D

The line * represents its &ertical component and it is denoted by Dy.The line 5* represents itshori'ontal component and it is denoted by D . 8ow in the triangle 5*

"inG *>5 MsinG Perpendicular>HypotonuseN

or sinG Dy>D

or F# Fsin

"imilarly

7osG 5*>5 MsinG *ase>HypotonusN

or 7osG D >D

or FG FCos

Dor the triangle

TanG *>5* MTanG per>hyp)

or TanG Dy>D


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or T$n+1 F#=FG

SUBTRACTION OF A ECTOR $%t is defined as the ddition of to the negati&e of a * is called the subtraction of a &ector ( *)$

KINE)ATICS.

DEFINITION$%t is the branch of Physics which deals with description of motion without reference to any opposingor e ternal force$.

KEINE)ATICS.

DEFINITION$%t is the branch of Physics which deals with description of motion without reference to any opposing

or e ternal force$.

)OTION$Bhen a body changes its position with respect to its surrounding so the body is said to be in the stateof motion$.TYPES OF )OTIONThere are three types of motion#10 Linear or Translatory motion20 9otatory motion

0 ibratory motion

1. *ine$r or Tr$nsl$tor# )otion%f a body mo&es in a straight path so the body is to be in Linear motion or Translatory motion.EG$m!le

bus is mo&ing on the road, person is running on the ground.

2. Rot$tor# )otion%f a body spins or rotates from the fi ed point ,so the body is to be in 9otatory motion.EG$m!leThe blades of a mo&ing fan, The wheel of a mo&ing car.

. i;r$tor# )otionTo and fro motion about the mean point so the body is to be in ibratory motion.EG$m!le

otion of a spring.

REST$Bhen a body does not change its position with respect to its surrounding so the body is said to be inthe state of rest$.EG$m!le

boo- is laying on the table, person is standing on floor, tree in the garden.

SPEED$The distance co&ered by a body in a unit time is called speed.$OR $The rate of change of distance is called speed.$

FOR)U*A"peed 4istance>Timeor S=t

UNITThe ".% unit of speed in .0." system is eter>second.

or m=s


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Kin5s O3 S!ee51. Uni3orm S!ee5%f a body co&ers an e+ual distance in e+ual inter&al of time so the body is said to be in uniform speed.

2. $ri$;le s!ee5%f a body does not co&er an e+ual distance in e+ual inte&al of time so the body is said to be in &ariable

speed.

E*OCITY$The distance co&ered by a body in a unit time in a particular direction is called &elocity.$OR $The rate of change of displacement is called speed.$OR $"peed in a definite direction is called &elocity.$

FOR)U*Aelocity 4isplacment>Time

or S=t

68%TThe ".% unit of elocity in .0." system is eter>second.or m=s

Kin5s O3 elocit#1. Uni3orm elocit#%f a body co&ers an e+ual distance in e+ual inter&al of time in a 7onstant direction so the body is saidto be in uniform elocity.

2. $ri$;le elocit#%f a body does not co&er an e+ual distance in e+ual inter&al of time in a particular direction so the bodyis said to be in &ariable &elocity.

ACCE*ERATION$The rate of change of &elocity is called acceleration.$OR $ cceleration depends upon the &elocity if the &elocity continously increases or decreases theaccelerattion will be produced.$

1. Positi9e Acceler$tion

%f the &elocity continously increases then the acceleration will be positi&e.2. Ne4$ti9e $cceler$tion %f the &elocity continously decreases then the acceleration will be negati&e.

FOR)U*Acceleration change of &elocity>Time

or a , 3+ i/=t

UNITThe ".% unit of elocity in .0." system is eter>secondOs+uareor m=S2

E UATION OF )OTIONThe relationship of initial &elocity, final &elocity, acceleration, time,and linear distance.

FIRST E UATION OF )OTIONsuppose an ob ect mo&es with initial &elocity $ i$ in a time $t$ and co&ers a distance $"$ in anacceleration $a$ and the final &elocity of an ob ect becomes $ f$

ccording to the defination of the acceleration $The rate of change of &elocity is called acceleration$i.e. cceleration 7hange of &elocity>time

I a f i>t


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DERI ATION

a f i>t

at f i

or 3 i $t

SECOND E UATION OF )OTIONccording to the definition of the acceleration $The rate of change of &elocity is called acceleration$.

i.e. cceleration 7hange of &elocity>time

I a f i>t

at f i

or f i O at (1)

"ubstituting the a&erage &elocity#

a& ( i O f)>/ (/)

The distance co&ered by the body in a unit#

" a&>t

Putting the &alue of a& from e+uation /#

" ( i O f)>/Q R t

Putting the &alue of f from e+uation 1#

" ( i O i O at)>/Q R t

" (/ i O at)>/Q R t

" ( i O at>/N R t

" ( it O 1>/at/) MHere / is the s+uare of the time $t$. 4ont write this sentence in the e aminationN

THIRD E UATION OF )OTIONccording to the definition of the acceleration $The rate of change of &elocity is called acceleration$.cceleration 7hange of &elocity>time

I a ( f i)>t

I at f i

or t ( f i)>a (1)

"ubsituting the a&erage &elocity#

a& ( i O f)>/ (/)

Be -now that#

a& ">t

I " a& R t

Putting the &alue of a& from e+uation / and &alue of t from e+ 1#

" ( i O f)>/Q R ( f i)>aQ


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" i/ f/>/a since M(aOb) (a b) a/ b/N

or 2$s 32 + i2

ACCE*ERATION DUE TO RA ITY OR FREE FA**IN OB@ECTS$:alileo was the first scientist to appreciate that, neglecting the effect of air resistance, all bodies in

free fall close to the Earths/$EG$m!le%f a ball is thrown &ertically upward, it rises to a particular height and then falls bac- to the ground.Howe&er this is due to the attraction of the earth which pulls the ob ect towards the ground$

CHARACTERISTIC OF FREE FA**IN BODIES10Bhen a body is thrown &ertically upward, its &elocity continously decreases and become 'ero at a particular height 4uring this motion the &alue of acceleration is negati&e and f is e+ual to 'ero (a ?. m>s/ , f 3).

20Bhen a body falls bac- to the ground , its &elocity continously increases and become ma imum at a particular height 4uring this motion the &alue of acceleration is positi&e and i is e+ual to 'ero (a ?. m>s/ , i 3).

0 cceleration due to gra&ity is denoted by a and its &alue is ?. m>s/ .

"0 E+uation of motion for the free falling bodies be written as,f i O gt

h it O 1>/ gt/

/gh f/ i/


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FORCE AND )OTION.

DYNA)ICS$%t is the branch of Physics which deals with causes of motion and their effects$

*A OF )OTIONS 8ewton formulated three laws of motion in his boo-.

NE TON FIRST *A OF )OTIONS 8ewton


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a 0 D>m

%f the alue of 0 is 1

so,

a D>m

or

F m$

10 FORCEDorce is an agent which produces motion in a body but some time force may not be succeeded to

produce motion in a body so we can say that the force is an agent which produces or tends to producemotion in a body.Be can further say that#

Dorce is an agent which stops or tends to stop the motion of a body. %n simple word we can also saythat force is an agent which changes or tends to change the sate of an ob ect.

2. )ASSThe +uantity of matter contained in a body is called mass. FOR)U*A

D ma

m D>a

68%T

The unit of mass in .0." system is 0ilograme (-g)

. EI HT%t is a force with which earth attracts towards its centre is called weight.

FOR)U*AB mg

68%T

The unit of weight in .0." system is 8ewton (8).

THIRD *A OF )OTION$ To e&ery action there is always an e+ual and opposite reaction $

E P*ANATIONccording to 8ewton


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boo-. The table as a reaction pushes the boo- upward. This is the reason thta the boo- is stationaryon the table and it does not fall down.

INERTIADe3inition$%nertia is the tendency of a body to resist a change in its state.$

EG$m!les7o&er a glass with a post card and place a coin on it. 8ow stri-e the post card swiftly with the nail ofyour finger. %f the stro-e has been made correctly, the postcard will be thrown away and the coin willdrop in the glass.%f a mo&ing bus stops suddenly, the passenger standing in it feels a er- in the forward direction. s aresult he may fall. %t is due to the fact that the lower part of the standing passengers comes to rest as the

bus stops. *ut the upper portion remains in motion due to inertia.

DIFFERENCE BET EEN )ASS AND EI HT)$ss1. The +uantity of matter present in a body is called mass.

/. The mass of a body remains constant e&erywhere and does not change by change in altitude.=. ass of a body possesses no direction. "o it is a scalar +uantity.A. ass can be determined by a physical balance.

ei4't1. The force with which the earth attracts a body towards its centre is called the weight of the body./. The weight of a body is not constant. %t is changed by altitude.=. Beight of a body has a direction towards the centre of the earth. "o it is a &ector +uantity.A. Beight can be determined by only a spring balance.

)O)ENTU)

$The +uantity or +uality of motion is called momentum and it is denoted by P$

)ATHE)ATICA* DEFINITION$%t is the product of mass and &elocity.$

)ATHE)ATICA* REPRESENTATIONP mwhere#S p is the momentumS m is the massS & the &elocity

*A OF CONSER ATION OF )O)ENTU)The law of conser&ation of momentum is a fundamental law of nature, and it states that the totalmomentum of a isolated system of ob ects (which has no interactions with e ternal agents) is constant.5ne of the conse+uences of this is that the centre of mass of any system of ob ects will alwayscontinue with the same &elocity unless acted on by a force outside the systemE A)P*E7onsider two bodies and * of mass m1 and m/ mo&ing in the same direction with &elocity 61 and6/ respecti&ely such that 61 is greater than 6/. "uppose the ball ac+uire &elocity 1 and /respecti&ely after collision

omentum of the system before collision m161 O m/6/

omentum of the system after collision m1 1 O m/ /

ccording to the law of conser&ation of momentum#

Total momentum of the system before collision Total momentum of the system after collision

m1U1 m2U2 m1 1 m2 2

FRICTION

De3inition


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$Bhen a body mo&es o&er the surface of another body then the opposing force is prodece and thisopposing force is called force of friction$

EG!l$n$tion"uppose a wooden bloc- is placed on a table and a spring balance is attached on it. %f we apply a &erysmall force of magnitude D by pulling the spring gradually and increase it, we obser&e that the bloc-

does not mo&e until the applied force has reached a critical &alue. %f D is less then critical &alue, the bloc- does not mo&e. ccording to 8ewton trying to ta-e place.

AD ANTA ES OF FRICTION10Be could not wal- without the friction between our shoes and the ground. s we try to step forward, we push your foot bac-ward. Driction holds our shoe to the ground, allowing you to wal-.20Briting with a pencil re+uires friction. we could not hold a pencil in our hand without friction.

0 nail stays in wood due to frction"0 8ut and bold cal hold due to friction

DISAD ANTA ES OF FRICTION10%n any type of &ehicle such as a car, boat or airplane e cess friction means that e tra fuel must be used to power the &ehicle. %n other words, fuel or energy is being wasted because of the friction.20The Law of 7onser&ation of Energy states that the amount of energy remains constant. Thus, the

energy that is $lost$ to friction in trying to mo&e an ob ect is really turned to heat energy. Thefriction of parts rubbing together creates heat.0 4ue to the friction a machine has less fre+uency 133W

"0 4ue to friction machine catch fire.

)et'o5s o3 Re56cin4 FrictionDriction can be reduced by the following methods#1. The &arious parts of the machines that are mo&ing o&er one another are properly lubricated.2. %n machines, the sliding of &arious parts is usually replaced by rolling. This id done by using ball bearings.

. Bhere sliding is una&oidable, a thic- layer of greasing material is used between the sliding surfaces.". The front of the fast mo&ing ob ects, e.g. cars, aeroplanes are made oblong to decrease air friction.


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*$? o3 FrictionSt$tement

The &alue of limiting friction increases proportionally with the increase in normal reaction. Hence,liming friction D(s) is directly proportional to the normal reaction.D(s) U 9 (Here U represents the sign of proportionality dont< write it in the e amination paper.)

I Ds u9 ........... (i)u D(s)>9

u is the constant of proportionality, which depends upon the nature of the surfaces of the two surfacesin contact. %t is -nown as the coefficient of friction. %t is only a number without any unit. Be -now thatthe normal reaction is directly proportional to the weight of the bloc-, therefore,9 B mg"ubstituting the &alue of 9 in e+uation (i)

I Fs 6m4

Rollin4 Friction%f we set a hea&y spherical ball rolling, it e periences an opposing force called rolling friction. Bhen a

body rolls o&er a surface, the force of friction is called rolling friction. 9olling friction is much lessthan the sliding friction. This is because the surfaces in contact are &ery much less.


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STATICS

DEFINITIONS1. St$tic"tatics deals with the bodies at rest under number of forces, the e+uilibrium and the conditions ofe+uilibrium.

2. Res6lt$nt ForceThe net effect of two or more forces is a single force, that is called the resultant force.

. )oment ArmThe perpendicular distance between the a is of rotation and the line of the action of force is called themoment arm of the force.

TOR UE%t is the turning effects of a force about an a is of rotation is called moment of force or tor+ue.

FACTORS ON HICH TOR UE DEPENDS1. The magnitude of the applied force.2. The perpendicular distance between a is of rotation and point of application of force.

9EP9E"E8T T%58Tor+ue may be represented as,Tor+ue Dorce R moment armT F J 5

CENTRE OF RA ITYThe centre of gra&ity is a point at which the whole weight of the body appears to act.

Centre o3 r$9it# o3 Re46l$r S'$!e5 O; ectsBe can find the centre of gra&ity of any regular shaped body ha&ing the following shapes#1. Tri$n4le7 The point of intersection of all the medians.2. Circle7 7entre of gra&ity of circle is also the centre of gra&ity.

. S:6$re7 Point of intersection of the diagnonals.". P$r$llelo4r$m7 Point of intersection of the diagonals.%. S!'ere7 7entre of the sphere.

Centre o3 r$9it# o3 Irre46l$r S'$!e5 O; ectsBe can find the center of gra&ity of any irregular shaped ob ect by using following method. 4rill a fewsmall holes near the edge of the irregular plate. 6sing the hole , suspend the plate from a nail fi edhori'ontally in a wall. The plate will come to rest after a few moments. %t will be in a position so thatits centre of gra&ity is &ertically below the point of suspension.

8ow, suspend a plumb line from the supporting nail. 4raw a line < in the plate along the plumb line.The centre of gra&ity is located somewhere on this line.9epeat the same process using the second hole *. This gi&es the line **< on the plate. lso repeat this

process and use hole 7 and get line 77


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CONDITIONS OF E UI*IBRIU)FIRST CONDITION OF E UI*IBRIU)$ body will be in first condition of e+uilibrium if sum of all forces along a is and sum of all forcesalong X a is are are e+ual to 'ero, then the body is said to be in first condition of e+uilibrium.$, FG F# /

SECOND CONDITIONS OF E UI*IBRIU)$ body will be in second condition of e+uilibrium if sum of cloc-wise( oment) tor+ue must be e+ualto the sum of anticloc-wise tor+ue( oment), then the body is said to be in second condition ofe+uilibrium.$S6m o3 tor:6e

STATES OF E UI*IBRIU)There are following three states of E+uilibrium#1. First St$te ,St$;le E:6ili;ri6m/

body at rest is in stable e+uilibrium if on being displaced, it has the tendency to come bac- to itsinitial position.

Bhen the centre of gra&ity of a body i.e. below the point of suspension or support, then body is said to be in stable e+uilibrium.

2. Secon5 St$te ,Unst$;le E:6ili;ri6m/%f a body on displacement topples o&er and occupies a new position then it is said to be in the state ofunstable e+uilibrium.Bhen the centre of gra&ity lies abo&e the point of suspension or support, the body is said to be in thestate of unstable e+uilibrium.

. T'ir5 St$te%f a body is placed in such state that if it is displaced then neither it topples o&er nor does it come bac-

to its original position, then such state is called neutral e+uilibrium.Bhen the centre of gra&ity of a body lies at the point of suspension, then the body is said to be inneutral e+uilibrium


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CIRCU*AR )OTION AND RA ITION

Centri!et$l ForceDe3inition$The force that causes an ob ect to mo&e along a cur&e (or a cur&ed path) is called centripetal force.$

)$t'em$tic$l EG!ressionBe -now that the magnitude of centripetal acceleration of a body in a uniform circular motions isdirectly proportional to the s+uare of &elocity and in&ersely proportional to the radius of the pathTherefore,a(c) U &/ (Here U represents the sign of proportionality do not write this in your e amination and /represents s+uare of &)a(c) U 1>r 7ombining both the e+uations#a(c) U &/>r

From Ne?tonLs Secon5 *$? o3 )otion7

D maI F,c/ m92=rBhere,S Dc 7entripetal DorceS m ass of ob ectS & elocity of ob ectS r 9adius of the cur&ed path

F$ctors on ?'ic' Fc De!en5s7Dc depends upon the following factors#S %ncrease in the mass increases Dc.

S %t increases with the s+uare of &elocity.S %t decreases with the increase in radius of the cur&ed path.EG$m!lesS The centripetal force re+uired by natural planets to mo&e constantly round a circle is pro&ided by the gra&itational force of the sun.S %f a stone tied to a string is whirled in a circle, the re+uired centripetal force is supplied to it by ourhand. s a reaction the stone e erts an e+ual force which is felt by our hand.S The pilot while turning his aeroplane tilts one wing in the upward direction so that the air pressuremay pro&ide the re+uired suitable Dc.

Centri364$l Force

De3inition$ force supposed to act radially outward on a body mo&ing in a cur&e is -nown as centrifugal force.$EG!l$n$tion7entrifugal force is actually a reaction to the centripetal force. %t is a well -nown fact that Dc isdirected towards the centre of the circle, so the centrifugal force, which is a force of reaction, isdirected away from the centre of the circle or the cur&ed path.

ccording to 8ewton


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)$t'em$tic$l EG!ressionTwo ob ects ha&ing mass m1 and m/ are placed at a distance r. ccording to 8ewtonr/ (Here / represents s+uare of r)

7ombining both the e+uations #

D U m1m/>r/

9emo&ing the sign of proportionality and introducing a constant#

F ,m1m2=r2/


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ORK0 ENER Y AND PO ER

De3initions1. @o6le%t is the wor- done by a force of one 8ewton when the body is displaced one meter.

2. Er4%t is the wor- done by a force of one 4yne when the body is displaced one centimeter.

. Foot Po6n5 ,3t+l;/%t is the wor- done by a force of one pound when the body is displaced one foot.

". Force%t is an agent that mo&es or tends to mo&e or stops or tends to stop a body.

%. $tt

Batt is the unit of power that is e+ual to the +uantity of 1 ;oule wor- done in 1 second.

or8 Bhen a force produces displacement in a body, it is said to do wor-.Units o3 or8

".% "ystem ;ouleS 7.:." "ystem ErgEG!l$n$tionBhen force is applied in the direction of the displacement we can find the wor- by using definitionBor- Dorce R 4isplacementB DRs

Fs"uppose a man is pulling the grass cutting machine then the direction of the foce and displacement isnot same. The applied force ma-es an angle G with the ground while the motion ta-es place along theground.

%n this case force is resol&ed into its components.D DcosGDy DsinG

s the machine mo&es along the ground, so D is doing the wor-, Hence#B Dorce R 4isplacementB DcosGRs

Fscos

Ener4#Energy is define as the capability to do wor-. Energy is also measured in ;oules."ome Types of EnergyS Potential EnergyS 0inetic EnergyS 7hemical EnergyS Heat EnergyS Light EnergyS 8uclear Energy

Potenti$l Ener4#De3initionThe energy possessed by a body due to its position is -nown as the Potential Energy of the body. %t isrepresented by P.E. and is measured in ;oules in "ystem %nternational.EG$m!lesThe energy of the following is potential energy#S bric- lying on the roof of a house.S The spring of a watch when wound up.S The compressed spring.S Bater stored up in ele&ated reser&oir in water supply system.


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)$t'em$tic$l EG!ression%f we lift a body of mass m to a height h, then the force applied on it is the its weight and it will actthrough a distance h."o,Bor- Dorce R 4istanceB B R h

"ince B mg, therefore#B mg R h"ince wor- is e+ual to energy possessed by a body#P.E. m4'

Kinetic Ener4#De3initionThe energy possessed by a body due to its motion is -nown as the 0inetic Energy of the body. %t isrepresented by 0.E.EG$m!lesThe energy of the following is -inetic energy#

S bullet fired from a gun.S railway engine mo&ing at high speed.S otion of a simple pendulum.

)$t'em$tic$l EG!ression7onsider a body of mass m at rest ( i 3) on a frictionless surface. Bhen a force D is applied, the

body co&ers a distance " and its final &elocity becomes f.To calculate the amount of wor- done, we apply the formula.B D R "

ccording to 8ewton/ (m&/)

Potenti$l Ener4#1. Energy possessed by a body by &irtue of its position is -nown as Potential Energy.2. *odies at rest ha&e Potential Energy.

. %t is calculated by P.E. mgh

*$? o3 Conser9$tion o3 Ener4#St$tementEnergy can neither be created, nor destroyed, but it can be con&erted from one form into the other.EG!l$n$tionconsider a body of mass mat height h abo&e the ground. %ts -inetic energy at that point is#


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0.E 1>/(m&/)0.E 1>/ m R (3)0.E 3 ........ (i)The potential Energy at point is #P.E mgh ............(ii)"o the total energy at point will be #

T.E 0.E O P.EE( ) 3 O mghE,A/ m4'

"uppose the body is released from this height and falls through a distance . %ts new height will be (h). The &elocity with which it reaches point * is calculated by using the third e+uation of motion#

/gs f/ i/s we -now#

S i 3S " Therefore,

/g f/ 3/g &/The -inetic energy at point * is#0.E. 1>/ m&/"ubstituting the &alue of &/#0.E. 1>/ R m R /g0.E mgThe Potential Energy at point * is#P.E mghThe height of the body is (h )#P.E. mg(h )The total energy at point * is #E(*) P.E O 0.E.E(*) mg O mg(h )E(*) mg O mgh mgE,B/ m4'Hence, the total energy at point and * are same. %t means that the total &alue of energy remainsconstant.

Po?erDe3initionThe rate of doing wor- is called power.

)$t'em$tic$l EG!ressionPower 9ate of doing Bor- Power Bor->TimeP =T

Unit o3 Po?erThe unit of Power is ;oules per second (;>s) or Batt (B).

Nee5 to Conser9e Ener4#The fuel that burns in running factories, transport and other acti&ities is mainly obtained from

underground deposits in the form of coal, oil, gas and other similar raw forms. These deposits arerapidly decreasing and one day all these resources of energy will be consumed. %t is therefore highlyimportant for us to a&oid wastage of energy.the consumption of two much energy is also ha&ing ad&erse effect on our en&ironment. The air in bigcities is hea&y because of pollution caused by industrial wastes and smo-e produced by automobiles.To ensure comfortable li&ing with a neat en&ironment, it is the responsibility of all of us as indi&idualsto conser&e energy.


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)ACHINES

2. )ec'$nic$l A59$nt$4eThe ratio between the resistance or weight to the power applied in a machine is called the mechanicalad&antage of that machine. %t is denoted by . .

. . Beight o&er comed by achine> Dorce pplied on the achine

. E33icienc#The ratio between the useful wor- done and the wor- done on the machine is called efficiency.

. (output>%nput) R 133

". In!6t%nput is the wor- done on the machine.

%. O6t!6t5utput is useful wor- done by the machine.

*e9erDe3initionLe&er is the simplest machine in the world. %t is a rigid bar, which can be rotated about a fi ed point.

Princi!le o3 *e9er%n the le&er the moment P acts opposite to that of wor- B. %t means that force D tends to rotate thele&er in one direction which the wight B rotates in opposite direction. %f the magnitude of thesemoments acting in opposite direction is e+ual, then the le&er will be in e+uilibrium. %t means that#

oment of P oment of B

)ec'$nic$l A59$nt$4eBe -now that according to Principle of Le&er#

oment of P oment of B

I Dorce R Dorce rm Beight R Beight rm

P R * B *7

*>*7 B>P

Hence,

. B>P *>*7 Beight rm> Dorce rm

Kin5s o3 *e9er1. First Kin5 o3 *e9er%n the first -ind of le&er, the fulcrum D is in the between the effort P and Beight B.EG$m!lesS Physical *alanceS Handle of PumpS Pair of "cissorsS "ee "aw

2. Secon5 Kin5 o3 *e9er%n the second -ind of le&er, the weight B is in between the fulcrum D and effort P.EG$m!lesS 4oorS 8ut 7rac-erS Punching achine

. T'ir5 Kin5 o3 *e9er

%n the third -ind of le&er, the effortP is in between the fulcrum D and weight B.EG$m!les


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S Human forearmS 6pper and Lower ;aws in the outh.S Pair of Dorecepes

Incline5 Pl$neDe3inition

hea&y load can be lifted more easily by pulling it along a slope rather than by lifting in &ertically."uch a slope is called an %nclined Plane.)ec'$nic$l A59$nt$4e

. B>P l>h Length of %nclined Plane>Perpendicular Height

P6lle# pulley consists of a wheel mounted on an a le that is fi ed to the framewor- called the bloc-. The

wheel can rotate freely in the bloc-. The groo&e in the circumference pre&ents the string from slipping.

FiGe5 P6lle#%f the bloc- of the pulley is fi ed then it is called a fi ed pulley.)ec'$nic$l A59$nt$4e o3 FiGe5 P6lle#%n a fi ed pulley, the force P is the applied force and weight B is lifted. %f we neclect the force offriction then#

Load Effort

%n the gi&en case#

Load B R Load rm

Load B R 5*

lso,

Effort P R Effort rm

Effort P R 5

"o,

BR5* PR5

I B>P 5 >5*

*ut, 5 5*, then

. B>P 5*>5*

).A 1

)o9e$;le P6lle#%n this pulley, one end of the rope that is passing around the pulley is tied to a firm support and effort Pis applied from its other end. The load and weight to be lifted is hung from the hoo- of bloc-. %n thissystem, the pulley can mo&e. "uch a pulley is called mo&eable pulley.)ec'$nic$l A59$nt$4e o3 )o9e$;le P6lle#%n an ideal system of a mo&eable pulley, the tension in each segment of the rope is e+ual to the appliedeffort. s two segments support the weight, the ffort acting on the weight B is /P. Therefore,according to the principle of le&er#

B R 9adius of the Bheel /P R 9adius of the Bheel

I /P B

The echanical d&antage is gi&en by#


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. B>P

. /P>P

M ).A 2Hence, the mechanical ad&antage of a mo&eable pulley is /.


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)ATTER

De3inition o3 )$tter$ nything ha&ing mass and &olume is called matter.$

Kinetic )olec6l$r T'eor# o3 )$tterThe 0inetic olecular Theory of atter has the following postulates#S atter is made up of &ery small particles called molecules.S These molecules are in the same state of motion, hence they possess -inetic energy. Their motion can

be translatory, &ibratory or rotational.S The molecules attract each other with a force. This force depends upon the distance between them.

Dorce is in&ersely proportional to the distance between the molecules.S Bhen a substance is heated its temperature as well as molecular motion increases. 4ue to this motion, -inetic energy also increases. we can say that when the -inetic energy of the molecules increases,then temperature of the substance rises.

Bro?ni$n )otion%n 1 /@, a scientist, 9obert *rown obser&ed the motion of molecules with the help of a microscope. Heobser&ed that the tiny particles in water are constantly mo&ing in a 'ig'ag path. He called the motion,*rownian otion.EG!l$n$tionThe cause of this tiny particle motion is the rapid motion of the molecules, which collide with the

particles and push them in one direction. %f some molecules come from other direction and collide withthe same particles, particles change their direction. This process continues and the motion becomes'ig'ag.

St$tes o3 )$tteratter has been classified into three states. These states are discussed below#

1.Soli5ccording to the -inetic theory of matter, solid has the least -inetic energy. The properties of solids are

gi&en below#S The particles are &ery close to each other.S Their shape and &olume is fi ed.S Particles in a solid &ibrate to and fro from their mean position.S 5n heating they melt and con&ert into li+uid.S "ome solids also con&ert directly into gas on heating.

2. *i:6i5ccording to the -inetic theory of matter, li+uids ha&e the following properties!

S They ha&e greater -inetic energy than solids but less than that of gases.S The &olume of li+uid is fi ed.S They mo&e more freely than solids.S The attraction between molecules is lower than solids.S The distance between the molecules is greater than that of solids.S 5n heating, they con&ert into &apours.S 5n cooling, they con&ert into solid.

. $sccording to the -inetic molecular theory, gases possess the following properties.

S :ases possess more -inetic energy.S Their shape and &olume are not fi ed.S The distance between their molecules is large.S Their temperature is proportional to their -inetic energy.S Their temperature rises with increase in pressure.S 5n cooling, they con&ert into li+uid and gases.

El$sticit#De3inition$ The tendency of a material to return to its original dimension after the deforming stress has beenremo&ed is -nown as elasticity.$


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%f we apply a force to a body, it is stretched. Bhen the applied force is remo&e, the body returns to itsoriginal shape. The phenomenon of turning bac- to its original shape is called Elasticity.

El$stic Be'$9io6r $n5 )olec6l$r T'eor#The elastic beha&iour of a material can be e plained by the 0inetic Theory of atter. "ince themolecules in a solid are &ery close to each other, there e ist strong attracting forces between them.

Thus when force is remo&ed, the attraction forces between the molecules pull them bac- again and thematerial is restored to its original shape. 4ifferent material ha&e different elasticity depending on thenature of the material.

El$stic *imitThe ma imum resisting force of a material is called the Elastic Limit of that material.

StressDe3inition$Bhen a body is made to change its length, &olume or shape by the application of an e ternal force,the opposing force per unit area is called "tress.$

Form6l$"tress Dorce > reao F=A (Here o represents (9ho) do not write in your e amination paper)

UnitsS ".% or 0" "ystem 8>m/ or Pascal (Pa)S 7.:." system 4yne>cm/S D.P." or *.E "ystem lb>ft/ and lb>in/(Here / in all abo&e systems shows s+uare)

T#!es o3 Stress

Dollowing are some types of stress#1. Tensile Stress7 %t is a stress tending to stretch a body.2. B6l8 Stress7 %t is an o&erall force per unit area, also -nown as pressure.

. S'e$r Stress7 %t is a stress tending to produce an angular deformation.

Str$inDe3inition"tress can produce a change in shape, &olume or length in an ob ect. This change in the shape of anob ect is called strain.Form6l$

athematically,

"train 7hange in Length>Length or "train 7hange in &olume > &olume

Units"ince strain is a ratio between two similar +uantities, it has no unit.

T#!es o3 Str$inDollowing are some types of strain.1. Tensile Str$in7 %t is a change in length di&ided by original length.2. B6l8 Str$in7 %t is the change in &olume di&ided by original &olume.

. S'e$r Str$in7 %t is e+ual to the angular displacement produced.

Hoo8Ls *$?Intro56ction

n English Physicist and 7hemist 9obert Hoo- disco&ered this law in 1C@ .St$tement$"train produced is proportional to the stress e erted within the elastic limit.$

El$stic *imitThe point at which a material becomes plastic is called elastic limit on yield point.

Yiel5 Pointthe yield point is the point at which the material begins to flow. %t is also the point between elasticregion and plastic region.


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El$stic Re4ionBhen the material obey reaP F=A

Unit

".% or .0." "ystem 8>m/ or Pascal.S 7.:." system 4yne>cm/.S D.P." or *.E "ystem lb>ft/ and lb>in/.

Press6re in *i:6i5s%n water or other li+uids, the weight e erted on a body or the bottom of the li+uid is its pressure.

P$sc$lLs Princi!leSt$tementBhen a pressure is applied to a li+uid contained in a &essel, it is transmitted undiminished e+ually inall directions and acts perpendicularly to the walls of the container.

A!!lic$tions + H#5r$6lic PressPascal


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HEAT

De3initions1. Intern$l Ener4#%nternal Energy of a body is the sum of all -inetic and potential energy of all molecules constituting the

body.

2. @o6les%t is the amount of heat re+uired to rise the temperature of 1>A/33 -g of pure water from 1A.2 7 to 12.27.

. C$lorie%t is the amount of heat re+uired to rise the temperature of 1 g of pure water from 1A.27 to 12.27.

". Britis' T'erm$l Unit%t is the amount of heat tht is re+uired to rise the temperature of 1 pound of pure water from C=D toCAD.

Di33erence Bet?een He$t $n5 Tem!er$t6reHe$t

Heat is the energy in transit from one body to another due to temperature difference.S %t is the total -inetic energy of the body.S Heat is measured using ;oule meter.S %ts unit is ;oule.

Tem!er$t6reS Temperature is the degree of hotness or coldness of a body.S %t is the a&erage -inetic energy of the body.S Temperature is measured using thermometer.S %ts units are D, 7 and 0.

T'erm$l EG!$nsionchange in length, breadth and height of a body due to heating is -nown as Thermal E pansion. %toccurs in all the three states, i.e. solids, li+uids and gases.

T'erm$l EG!$nsion o3 Soli5s"olids e pand on heating. Their ability to e pand depends on their molecular structure. s the

temperature is increased, the a&erage -inetic energy of the molecules increases and they &ibrate withlarger amplitudes. This results in increase in the distance between them. Hence, they e pand onheating. Thermal E pansion of solids can be classified into three types.

1. *ine$r T'erm$l EG!$nsion7hange in length or any one dimension of a solid on heating is -nown as L%near Thermal E pansion.

2. Re$l EG!$nsionThe sum of the obser&ed increase in the &olume of a li+uid and that of the containing &essel is calledreal Thermal e pansion.9eal E pansion pparent E pansion O E pansion of the essel

. A!!$rent EG!$nsionpparent E pansion is the e pansion in which only the e pansion of li+uid is considered and

e pansion of the &essel is not ta-en into account. pparent e pansion is less the real e pansion.

Anom$lo6s EG!$nsion o3 $terThe increase in the &olume of water as its temperature is lowered from A 7 to 37 is -nown asanomalous e pansion of water.

E33ects o3 Anom$lo6s EG!$nsion o3 $ter1. %n winter, the temperature in the north and south poles of the earth falls. s the temperature fall

below A 7 water on the surface e pands and stays afloat. %ce continues building up at the surface


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while the temperature at the bottom remains at A 7. This helps fish and other forms of marine life toli&e.2. 4uring the rainy season a lot of water seeps through the crac-s in the roc-s. %n winter, when thewater e pands, the roc- get bro-en due to this e pansion.

. %n cold climate, water supply pipes burst when the water e pands on cooling.

AS *A S1. Bo#leLs *$?The &olume of a gi&en mass of a gas is in&ersely proportional to the pressure, %f the temperature is -eptconstant.

P U 1> (Here U represents sign of proportionality. 4o not write this in your e amination paper)

P 7 R 1>

C P

The abo&e e+uation is -nown as e+uation of *oyle


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or8in4Bhen the bulb is heated, the li+uid in it e pands and rises in the tube. temperature scale is mar-ed onthe glass stem to indicate temperatures according to the &arious le&els of li+uid in the tube.

2. Clinic$l T'ermometerIntro56ction

clinical thermometer is a de&ice that is used to find the temperature of the human body. %t has a rangefrom =2 7 to A= 7 (?2D to 113D).

Constr6ction%t consists of a glass stem with a capillary tube, ha&ing a small bulb at one end. This bulb is filled witha li+uid usually mercury or alcohol colored with a red dye. The upper end of the capillary tube issealed so that the li+uid will neither spill nor e&aporate. The air from the capillary tube is alsoremo&ed. The glass stem of a clinical thermometer has a construction in its capillary tube near the bulb.This helps to stop the mercury thread from mo&ing bac- when the thermometer is remo&ed from the

patient


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1. Bi+met$l T'ermometerIntro56ction

bi metal thermometer is made of a bi metallic coil. 8o li+uid is used in such type of thermometer.

Constr6ction%t consists of a bi metallic strip in the form of a long spiral. 5ne end of the spiral is -ept fi ed, while a

light pointer is attached to the other end.

or8in4Bhen the temperature rises, the bi metal strip coil itself into an e&en tighter spiral due to differente pansion rates of the two metals. the pointer mo&es across the temperature scale and in this wayreading is noted.

2. Fire Al$rmIntro56ction

fire alarm is used to warn people when there is a fire.

Constr6ction%n a fire alarm, one end of a bi metal strip is firmly fi ed, while the other is free. 5ne terminal of a C&olt battery is connected to the fi ed end of the strip through a C &olt bulb or bell. The other terminal of the battery is connected with a metallic contact which is ust abo&e the free end of the bi metallic strip.

or8in4Bhen a fire starts, heat energy is gi&en off. %t raises the temperature of the bi metallic strip and its freeend bends towards the contact. 5n touching the contact, electric circuit gets completed and the bulbstarts to glow or in case of a bell, it rings warning about the fire.

*$tent He$t o3 F6sionThe +uantity of heat re+uired to transform 1 -g of ice completely melts into water at 37 is -nown asLatent Heat of Dusion.

*$tent He$t o3 $!ori


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F$ctors on ?'ic' E9$!or$tion De!en5sE&aporation depends on the following factors#1. 8ature of Li+uid# %f the boiling point of a li+uid is low, then they e&aporate much +uic-ly e.g.

lcohol and Ether.2. Temperature of Li+uid# %f the surface temperature of a li+uid is increased, then rate of e&aporationalso increases, e.g. ironing of clothes.

. "urface rea of Li+uid# %f the surface area of a li+uid is increased, then the rate of e&aporation increases, e.g. li+uids spread o&er large areas e&aporate more +uic-ly.". 4ryness of ir# %f there is more dryness in the air, then the rate of e&aporation increases, e.g. inhumid weather, clothes ta-e a longer time to dry.%. Bind speed# %f the wind speed is greater, then e&aporation rate increases.&. ir Pressure on the "urface of The Li+uid# %f the pressure on the surface of the li+uid is increased,the rate of e&aporation decreases.

*$? o3 He$t EGc'$n4eDor an isolated system comprising mi ture of hot and cold substances, the heat lost by hot substancesis e+ual to the heat gained by cold substances.

Heat lost by hot body Heat gained by cold body

Re3ri4er$torIntro56ction

refrigerator is a de&ice that is used to -eep fruits, &egetables and other eatables cool.

Constr6ction refrigerator consists of a compressor, condenser and e&aporator.

Re3ri4er$ntDreon is used as the refrigerant in a referigerator. This gas li+uifies at normal temperature if the

pressure is increased.

or8in4

1. 7ompression# Dreon gas is first compressed in the compressor of a refrigerator. %t is then fed into the condenser.2. 7ondensation# %n the condenser, the gas is li+uified under pressure. %t con&erts into a li+uid atnormal temperature. This gas is then allowed to pass through a &al&e into the e&aporator.

. E&aporation# The pressure in the e&aporator is comparati&ely less than in the condenser. Therefore, when li+uid Dreon enters the e&aporator, it e&aporates absorbing a large amount of heat. This resultsin cooling the area around the e&aporator. This is where we -eep our eatables.

(4iagram)The gas is then again fed into the compressor and the process continues.


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A ES AND SOUND.

De3initions1. i;r$tion5ne complete round trip of a simple harmonic motion is called &ibration.or%f a body in periodic motion mo&es to and fro o&er the same path, this motion is called 5scillation.

2. Time Perio5 ,T/The time re+uired to complete &ibration is -nown as time period.

. Fre:6enc#%t is the number of &ibrations e ecuted by an oscillating body in one second.

". Dis!l$cement%t is the distance of a &ibrating body at any instant from the e+uilibrium position.

%. Am!lit65eThe ma imum distance of the body on either side of its e+uilibrium position is -nown as amplitude.

&. $9e *en4t'The distance between two consecuti&e crests and troughs is called wa&elength.

(. N$t6r$l Fre:6enc#The fre+uency at which an ob ect will &ibrate freely (without any e ternal periodic force or resistance)is -nown as natural fre+uency of that ob ect.

>. A65i;le So6n55ur ear can hear only those sounds whose fre+uency is between /3H' and /3333H'. This range is-nown as audible sound.

-. Ultr$sonic So6n5"ound with fre+uency greater than /3333 H' is -nown as ultrasonic sound.

1 . Oct$9eThe inter&al between a wa&eform and another of twice the fre+uency is -nown as 5cta&e.

UnitsFre:6enc#7 7ycles per second (eps) or Hert' (h')

$9elen4t'7 eter Intensit# o3 So6n57 Batt>meter/ or B>m/Noise7 4ecibel (4*)

Sim!le H$rmonic )otion ,S.H.)/De3inition$To and fro motion of a body in which acceleration is directly proportional to displacement and alwaysdirected towards mean position is -nown as "imple Harmonic otion.$

Con5ition 3or S.H.)The conditions for simple Harmonic otion are gi&en below#S "ome resisting force must act upon the body.S cceleration must be directly proportional to the displacement.S cceleration should be directed towards mean position.S "ystem should be elastic.EG$m!lesDollowing are the e amples of ".H. #S *ody attached to a spring hori'ontally on an ideal smooth surface.S otion of a simple and compound pendulum.S otion of a swing.S otion of the pro ection of a body in a circle with uniform circular motion.


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Reson$nceDe3inition$The large amplitude &ibration of an ob ect when gi&en impulses at its natural fre+uency is -nown as9esonance.$EG!eriment7onsider a long string stretched tightly between two pegs. Dour pendulums , *, 7 and 4 of different

lengths are fastened to the string. nother pendulum E of same length as is also fastened.Bhen pendulum E is set to &ibrate, it will be obser&ed that all the pendulums start to swing but pendulum begins to &ibrate with larger amplitude, as pendulum E is set into &ibration. %t imparts itsmotion to the string. This string in turn imparts the same periodic motion to the pendulums. The naturalfre+uency of all other pendulums e cept is different. 4ue to the same natural fre+uency only &ibrates as the same &ibration of E. This phenomenon under which pendulum begin to &ibrate iscalled resonance.EG$m!le

arch of "oldiers while 7rossing the *ridgeEach bridge has its own natural fre+uency and marching of soldiers is another &ibrating system. "othere may occur a force on &ibration in bridge. This may damage the bridge. "o, for safely precautions,

it is written that soldiers must march out of stop while crossing the bridge.

$9eDe3inition$ method of energy transfer in&ol&ing some form of &ibration is -nown as a wa&e.$

$9e )otionBa&e motion is a form of disturbance, which tra&els through a medium due to periodic motion of

particles of the medium about their mean position.EG!erimentBe see that if we dip a pencil into a tap of water and ta-e it out a pronounced circular ripple is set up

on the water surface and tra&els towards the edges of the tub. Howe&er if we dip the pencil and ta-e itout many times, a number of ripples will be formed one after the other.Ba&es can also be produced on &ery long ropes. %f one end of the rope is fi ed and the other end isgi&en sudden up and down er-, a pulse shaped wa&e is formed which tra&els along the rope.

Tr$ns9erse $9eDe3inition$The wa&e in which amplitude is perpendicular to the direction of wa&e motion is -nown as Trans&erseBa&e.$EG$m!les

9adio Ba&es

S Light Ba&esS icro Ba&esS Ba&es in BaterS Ba&es in "tring

*on4it65in$l $9eDe3inition$The wa&e in which amplitude is parallel to wa&e motion is called longitudinal wa&e.$EG$m!le

"ound Ba&esS "eismic Ba&es

So6n5De3inition$ &ibration transmitted by air or other medium in the form of alternate compressions and rarefactionsof the medium is -nown as "ound.$

Pro56ction o3 So6n5"ound is produced by a &ibrating body li-e a drum, bell, etc, when a body &ibrates. due to the to andfro motion of the drum, compressions and rarefactions are produced and transmitted or propagated inair.


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Pro!$4$tion o3 So6n5 $9esBhen a body &ibrates in air, it produces longitudinal wa&es by compressions and rarefactions. Thesecompressions and rarefactions are tra&eled by the particles of the medium and transferred into the ne t

particles. 4ue to this transference, sound propagates in a medium.EG!eriment(4iagram)

"uspend an electric bell in a ar by its wires through a cor- fi ed in its mouth. "witch on the bell, wewill hear the sound of the bell. 8ow start remo&ing air from ar with the help of an e haust (&acuum) pump. The sound will decrease, although the hammer is still seen stri-ing the bell. This e perimentshows that air or any other medium is necessary for the propagation of sound.

elocit# o3 So6n5%t is a matter of common e perience that the flash of lightning is seen earlier than hearing the thunderof cloud. "imilarly when a gun is fired its sound is heard a little after seeing its flash. The reason is thatlight is faster than sound. 4ue to its slow &elocity sound lags behind.EG!eriment"elect two stations at a distance of -m (or any more distance) such that there is no obstacle between

them. Dire a gun at station and note the time of sound ta-en for such distance. 9epeat the process andnote the time ta-en by the sound to tra&el from * to . %f we substitute the mean of the two timesrecorded and distance " ( -m) in the formula ">t, we will get the &elocity of sound.

F$ctors E33ectin4 elocit# o3 So6n5The factors are gi&en below#S elocity of air or any other medium.S 4ensity of the medium.S Temperature of the medium.S 8ature of the medium

C'$r$cteristics o3 So6n5The characteristic properties of sound by which we can distinguish between noise and music, shrill andgra&e sounds or sound of men and women are -nown as characteristics of sound. The properties ofsound are gi&en below#

1.*o65nessDe3inition$Loudness is the magnitude of auditory sensation produce by sound.$%ntensity can be defined as the energy carried by the sound wa&es through a unit area placed

perpendicular to the direction of wa&er per second.

F$ctors E33ectin4 *o65ness o3 So6n5Loudness depend on following factors#Are$ o3 i;r$tion o3 Bo5#7 :reater will be the surface area more will be the loudness.Am!lit65e o3 )otion o3 i;r$tin4 O; ect7 :reater will be the amplitude, more will be the loudness.Densit# o3 )e5i6m7 Loudness is directly proportional to the density of medium.)otion $n5 Direction7 %f source of sound is mo&ing towards the listener loudness will be greater or ifwind supports the &elocity of sound the loudness will be greater.

2. Pitc'De3inition$The sensation that a sound produces in a listener as a result of its fre+uency is -nown as Pitch.$

This is the property of sound by &irtue of which we can distinguish between a shrill and gra&e sound.

F$ctors E33ectin4 Pitc' o3 So6n5Pitch depends on following factors#

Fre:6enc# o3 i;r$tin4 Bo5#7 The greater the fundamental fre+uency, more shrill will be the sound.

Rel$ti9e )otion o3 So6n57 %f source and listener both are coming closer pitch will increase.

. 6$lit# or Tim;re or ToneDe3inition$The characteristic of a musical note that is determined by the fre+uency present is -nown as Fuality

or Timbre or Tone of that sound.$


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This is the property of sound by &irtue of which it is possible to identify a sound of the same loudnessand pitch but originating from different instrument.

F$ctors E33ectin4 6$lit#Fuality depends upon the following factors#S Phase of the "ound Ba&e.

S "hape of Ba&es

H$rm36l E33ects o3 So6n5 ,Noise/ 8owadays noise is considered as a great pollution, which is &ery dangerous for us. "ome of them areas follows#S 7ontinuous noise damages hearing and can result in complete deafness.S 8oise has become a great cause for depression and blood pressure.S ental system shows less efficiency due to noise.S 7onse+uently it is harmful in all respects for li&ing body.

)6sic$l So6n5The sound producing pleasing effect on our ears are called musical sounds.

Di33erence Bet?een *on4it65in$l $n5 Tr$ns9erse $9es*on4it65in$l $9es1. %n longitudinal wa&es, particles of the medium &ibrate in the direction of the wa&es.2. The portion of wa&e in which particles of medium are &ery close to each other is calledcompression.

. E amples of longitudinal wa&es are sound wa&e and seismic wa&es.". 4istance between the centre of two compressions and rarefactions is called wa&elength.

Tr$ns9erse $9es

1. %n trans&erse wa&es, particles of the medium &ibrate in the direction perpendicular to the direction of wa&e.2. The portion in which particles of medium are higher than their normal position is called crest.

. E amples of trans&erse wa&e are microwa&es and radio wa&es.". 4istance between two crests and troughs is called wa&elength.


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PROPA ATION AND REF*ECTION OF *I HT

De3initions1. Inci5ent R$#The ray that stri-es the surface of the medium is -nown as %ncident 9ay.

2. Re3lecte5 R$#The ray that is sent bac- into the same medium after reflection is -nown as reflected ray.

. Pl$ne )irror flat smooth reflecting surface, which shows regular reflection is -nown as plane mirror.

". Norm$lPerpendicular line on the reflecting surface is -nown as normal.

%. PoleThe centre of the spherical mirror is called pole.

&. An4le o3 Inci5enceThe angle subtended by the incident ray to the normal is -nown as angle of incidence.

(. An4le o3 Re3lectionThe angle subtended by the reflected ray to the normal is -nown as angle of reflection.

>. Center o3 Re3lectionThe center of the hollow sphere of which the mirror is a part is called center of cur&ature.

-. Princi!le AGisThe straight line passing through center of cur&ature nad the pole is -nown as principle a is.

1 . Princi!le Foc6sThe ray coming parallel to principal a is after con&erges to or di&erges from a point, which is called

principle focus.

11. Foc$l *en4t'The distance between the principle focus and pole of the mirror is called Docal Length.

12. R$5i6s o3 C6r9$t6reThe distance between the center of cur&ature and the pole is called radius of cur&ature.

1 . Re$l Im$4ethe image that can be seen on a screen is -nown as a real image.

1". irt6$l Im$4eThe image that cannot be seen on a screen is -nown as a &irtual image.

1%. )$4ni3ic$tionThe ratio between the image height and ob ect height is -nown as magnification.The ratio between the image distance to the ob ect distance is -nown as magnification.

Re3lection o3 *i4'tDe3inition$The process in which light stri-ing the surface of another medium bounces bac- in the same mediumis -nown as 9eflection of Light.$

*$?s o3 Re3lection1. The angle of reflection, is e+ual to the angle of incidence# nUi mUr.2. The incident ray, reflected ray and normal, all lie in the same plane.


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Kin5s o3 Re3lectionThere are two types of 9eflection#

1. Re46l$r Re3lectionDe3initionBhen parallel rays of light stri-e a surface and most of them are reflected in a same particular direction

or same angle, they are said to be regularly reflected and the phenomenon is -nown as regularreflection.9egular reflection occurs when parallel rays of light stri-e with an ideal smooth plane surface. %nregular reflection parallel rays remain parallel after reflection.

2. Irre46l$r Re3lectionDe3initionBhen some rays of light stri-es a surface and the reflected rays scatter in different directions, this typeof reflection is called irregular reflection.%t occurs when parallel rays stri-e with an irregular rough surface. %n this case rays does not remain

parallel after reflection and they scattered.

A59$nt$4es o3 Irre46l$r Re3lection4ue to this reflection, sunlight reaches us before sunrise and persists for some time e&en after the

sunset.S 4ue to this reflection we get sufficient light in our rooms and other places where sunlight do notreach directly.S 4ue to this reflection sunlight reaches to each of the lea&es of a tree and photosynthesis ta-es placeon large scale.S 4ue to this reflection, we can see luminous ob ects.

Im$4e Forme5 ;# $ Pl$ne )irror7onsider a mirror


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Pro!ertiesThe bulging side is polished.

S 9eflection occurs from its hollow side.S They con&erge the parallel rays at a point.S They can form real and imaginary, both type of images.

Form$tion o3 Im$4e ;# Conc$9e )irrorsThere are si cases to form an image by conca&e mirror.

1. O; ect $t In3init#(4iagram)%f the ob ect is placed at infinity from the mirror, the rays coming from the ob ect are parallel to

principal a is. fter reflection, they meet at principal focus and image is formed at the focus.

Det$ils o3 Im$4eDormed at D.

S E tremely "mall

S 9ealS %n&erted

2. O; ect Be#on5 C(4iagram)%f the ob ect is placed beyond 7, rays coming from the ob ect are not parallel. They meet afterreflection between the focus and center of cur&ature. Therefore, image is formed between the focus andcenter of cur&ature.

Det$ils o3 Im$4eDormed between D and 7.

S "mall in si'e.S 9ealS %n&erted

. O; ect $t Center o3 C6r9$t6re LCLBhen ob ect is placed at the centre of cur&ature, the image formed at the same place.(4iagram)

Det$ils o3 Im$4eDormed at 7

S E+ual in si'e

S 9ealS %n&erted

". O; ect Bet?een F $n5 C(4iagram)Bhen the ob ect is placed between the focus and 7entre of cur&ature, the image is formed beyond thecentre of cur&ature.

Det$ils o3 Im$4e Dormed beyond 7.

S Large in si'e.S 9ealS %n&erted

%. O; ect $t F(4iagram)Bhen ob ect is placed at focus the reflected rays become parallel to each other. The two parallel linesmeet at infinity. Therefore, we say the image is formed at infinity.

Det$ils o3 Im$4eDormed at %nfinity.

S E tremely Large


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S 9ealS %n&erted

&. O; ect ;et?een P $n5 F(4iagram)Dor locating ob ect between pole and focus the rays reflected do not meet because they di&erge. *ut

they meet bac-ward. "o, the image is formed bac-ward or behind the mirror.

Det$ils o3 Im$4eDormed behind the mirror.

S Large in si'eS irtualS Erect

Uses o3 S!'eric$l )irror"pherical mirrors are used in se&eral places. "ome of them are gi&en below#

S'$9in47 conca&e mirror is used to enlarge the image. )icrosco!e7 con&e mirror is used for magnification in a microscope. Telesco!e7 The con&e mirror is used. In Se$rc'li4'ts $n5 He$5li4'ts7 7onca&e mirror is used to form the rays in searchlights and

headlights, used for different purposes. For Re$r ie?7 The con&e mirror is used in automobiles. In )e5ic$l EG$min$tion ,O!t'$lmosco!e/7 4octors use conca&e mirror for the e amination of ear,

nose, throat and eyes of patients.


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REFRACTION OF *I HT AND OPTICA* INSTRU)ENTS

De3initions1. Emer4ent R$#The ray after passing the second medium comes again in the first medium. %t is called emergent ray.

2. Emer4ence An4leThe angle formed by the emergent ray and normal is called emergence angle denoted by Ue.

. O!tic$l CenterThe middle point of the lens is called optical center. The ray passing through this point does not bend.

". Accommo5$tionThe ability of the eye to change the focal length of its lens so as to form a clear image of an ob ect onits retina is called is power of accommodation.

%. Persistence o3 isionBhen an ob ect is seen by an eye, its image forms on retina. %f the ob ect is remo&ed, the impression of image persists in the eye for about 1>13 second. This inter&al is called Persistence of ision.

&. Po?er o3 *ensThe power of the lens is the reciprocal of the focal length measured in meter. %ts unit is 4ioptre.

Re3r$ction o3 *i4'tDe3inition$The change in the direction and &elocity of light as it enters from one medium to another is -nown as

9efraction of Light.$

*$?s o3 Re3r$ctionThe incident ray, refracted ray and the normal at the point of incidence all lie in the same plane.

S The ratio of sine of angle of incidence (i) to the sine of angle of refraction (r) is constant for all raysof light from one medium to another. This constant is -nown as 9efracti&e %nde (u). This ratio isalso e+ual to the ratio of the speeds of light in one medium to another.9efracti&e %nde sinUi>sinUr "peed of light in first medium>"peed of light in second medium

Re3r$cti9e In5eGThe ratio between the sine of the angle of incidence to the sine of angle of refraction is -nown as

9efracti&e %nde .

9efracti&e %nde sin Ui>sinUr

SnellLs *$?The refracti&e inde between two particular mediums is e+ual to the ratio of speed of light in firstmedium and speed of light in second medium e+ual to the ratio between sin Ui and sin Ur.9efracti&e %nde sinUi>sinUr "peed of light in first medium>"peed of light in second medium

PrismDe3inition$Prism is a transparent piece of glass. %t has three rectangular sides and two triangular sides.

Re3r$ction T'ro64' $ Prism(4iagram)where,S Ui angle of incidenceS Ur angle of refractionS Ue angle of emergenceS U4 angle of de&iation

Tot$l Intern$l Re3lection(4iagram)


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%f the &alue of angle of incidence is increased so much so that it becomes greater than tht of the criticalangle then no more refraction occurs but on the other hand refracted ray again comes bac- in thedenser medium. ctually at that time, the surface of denser medium acts as a plane mirror and theincident ray bends in the same medium. This phenomenon is called Total %nternal 9eflection. %t is usedin Periscope, 5ptical Dibers and other instruments.

Tot$l Re3lectin4 PrismTotal internal reflection is used in prism. %n prism the angle between two opposite sides is ?3 and othertwo angles are A2 each. %f we arrange a ray so that it falls perpendicular to the * side then it willrefract without bending and stri-e the side 7 with angle A2. Then it totally reflects to the side *7.

Con5itions 3or Tot$l Intern$l Re3lectionThe ray of light should tra&el from denser to rarer medium.

S The angle of incidence should be greater than the critical angle.

*ensesDe3inition

transparent and smooth glass or any refracting medium surrounded by two spherical surfaces is-nown as lens.

T#!es o3 *ensesThere are two types of lenses#

1. Con9eG *ens%f the glass is thic- at the center and thin at the edges then it is -nown as con&e lens. %t is a con&erginglens.(4iagram)%t has three types#

S 4ouble 7on&e LensS Plano 7on&e LensS 7onca&o 7on&e Lens

2. Conc$9e *ens%f the lens is thinner in the center and thic-er at the edges then it is -nown as a conca&e lens. %t is adi&erging lens.(4iagram)%t has three types#S 4ouble 7onca&e LensS Plano 7onca&o Lens

S 7on&e 7onca&e Lens

Form$tion o3 Im$4e ;# Con9eG *ens1. O; ect $t In3init#Bhen ob ect is placed at infinite distance from con&e lens the rays coming from the ob ect are parallelto each other and they meet after refraction at the focus.

Det$ils o3 Im$4eS Dormed at DocusS 9ealS%n&ertedS t opposite sideS Highly diminished

2. O; ect Be#on5 2FBhen ob ect is placed at some distance from /D then image is formed between the focus and center ofcur&ature (/D).

Det$ils o3 Im$4e*etween D and /D

S 5pposite side of LensS 9eal


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S %n&ertedS "mall in si'e

. O; ect $t 2FBhen ob ect placed at center of cur&ature, image is formed at center of cur&ature at the opposite side.

Det$ils o3 Im$4e9ealS %n&ertedS t /DS "ame in si'eS t the opposite side of the Lens

". O; ect ;et?een F $n5 2FBhen ob ect is placed between the focus and center of cur&ature then the image is formed on oppositeside beyond the center of cur&ature.

Det$ils o3 Im$4e9eal

S %n&ertedS Large in si'eS 5pposite side of lensS *eyond /D

%. O; ect $t FBhen ob ect is placed at focus the refracted rays are parallel to each other and meet at infinity.

Det$ils o3 Im$4e

9ealS %n&ertedS E tremely LargeS 5pposite side of LensS t infinity

&. O; ect ;et?een F $n5 OBhen ob ect is placed between the lens and principal focus, then the refracted rays does not meet atopposite side but image is formed at the same side where the ob ect is placed.

Det$ils o3 Im$4e

irtualS ErectS LargeS "ame side of lensS *eyond the ob ect

O!tic$l Instr6ments1. THE EYE(4iagram)

F6nctions o3 t'e P$rts o3 E#e1. Scler$ Scelortic%t is a layer enclosed in ca&ity filled with a fluid called itrous Humour. %t is the outer coating of eye.

2. C'oroi5%t is a dar- membranous coating. This is coated with blac- pigments. %t -eeps the inner parts of the eye

ball light proof.

. Retin$%t is semi transparent membranes of ner&e fibers forming the innermost coating of the eye andsensiti&e to light. %t is a screen on which image is formed.


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". Corne$%t allows light into the eyes. %t is transparent and bulging in shape.

%. Iris%t is li-e diaphragm of a camera. %t has a tiny opening at its center called pupil, which regulates the+uantity of light entering the eye.

&. Cr#st$lline *ensThis is a lens that automatically contracts and e pands, alters the focal length of eye lens.

(. Cili$r# Bo5#%t holds crystalline lens in the proper position.

>. A:6eo6s H6mo6r $n5 itro6s H6mo6rThe place between cornea and the lens is filled by a transparent li+uid called +ueous Humour. Thelarge chamber of the eye between the lens and the bac- of eye is filled with a elly li-e substance called

itreous Humour. These li+uids ser&e mainly to -eep the spherical shape of the eye.

)$in De3ects o3 E#e1. S'ort Si4'te5ness ,)#o!i$/%f a person can see ob ect placed near, but cannot see distant ob ect, this defect is -nown as shortsightedness.

C$6sesThis defect appears due to increase in thic-ness of eyeball. The focal length decreases ma-ing theimage to form before retina.(4iagram)

Remo9$l o3 De3ect%t is remo&ed by using a conca&e lens of suitable focal length.(4iagram)

2. *on4 Si4'te5ness ,H#!ermetro!i$/%f a person can see distant ob ects, but not near ob ects, this defect is called long sightedness.C$6sesThis defect appears due to decrease in thic-ness of ball. The focal length increases so that the image isformed beyond the retina.(4iagram)

Remo9$l o3 De3ect%t is remo&ed by sing a con&e lens of suitable focal length.(4iagram)

. Asti4m$tism%t is the defect in which the clear image of an ob ect does not form on the retina.C$6sesThis defect appears due to non sphericity of the cornea.

Remo9$lThis defect can be remo&ed by using lenses of different focal length.

". Pres;#o!i$The accommodation power of eye loses by which a person suffers a long sightedness. This defect iscalled Presbyopia or Lac- of ccommodation.C$6sesThis defect appears due to loss of accommodation power of the lens of the eye.

Remo9$lThis defect can be remo&ed by using con&e lens.


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2. CA)ERADe3inition

camera is an optical de&ice for obtaining still photographs or for e posing cinematic films.

Constr6ction%t consists of a light proof bo with a lens at one end and a photographic plate or film at other end and

a shutter to control the light rays.

or8in4To ma-e an e posure, the shutter is opened and an image is formed by lens on the photographic plateor film, small in si'e. Photographic plate or film sa&es this image. %n this way an image is obtained.

. CO)POUND )ICROSCOPEConstr6ction%t consist of two con&e lenses at the end of two tubes. 5ne tube can slide into other so that thedistance between them can be change. The lens near the ob ect is the small con&e lens of short focallength is called ob ecti&e. The lens near the eye is the larger con&e of longer focal length is called

eyepiece.(4iagram)

or8in4The ob ect is placed between D and GD and its real, in&erted and magnified image


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NATURE OF *I HT AND E*ECTRO)A NETIC SPECTRU)

De3initions1. D6$l N$t6re o3 *i4'tLight has dual nature, it beha&es not only as a particle (photon) but also as a wa&e. This is called dual

nature of light.

2. Dis!ersion o3 *i4'tBhen a beam of sunlight falls on a prism, the light is split up in se&en colours. This phenomenon iscalled 4ispersion of Light.

. R$in;o?The rainbow is an arc of spectral colours formed across the s-y during or after rainfall in the morningor when the sun is behind us.

". P'otons , 6$nt6m/Photons are tiny pac-ets of energy. They beha&e as particles but actually they are not particles.

8ewton


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)icro?$9esThese radio wa&es ha&e shorter wa&elength between 1mm and =33 mm. icrowa&es are used in radarsand o&ens.

In3r$re5 $9es%t has a long range. %ts mean wa&elength is 13 micrometers.

isi;le $9es%t has a range of A33 nm to @33 nm.

Ultr$9iolet $9esTheir wa&elength ranges from = 3nm onwards. These are emitted by hotter start (about /2333 7).


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E*ECTRICITY

De3initions1. Ins6l$torsThose material ob ects that do not allow charge to pass through them are -nown as %nsulators or non

conductors.

2. Con56ctorsThose material ob ects that allow the charge to pass through them are called conductors.

. Semi Con56ctorsThose material ob ects that allow some charge to pass through them are called "emi 7onductors.

". Free ElectronThose electrons that are loosely bound by their atom and can mo&e freely within the material are calledfree electrons.

%. DielectricThe medium or space (&acuum) between two charges is said to be dielectric.

&. Force o3 Attr$ctionBhen two charges attract each other the force is called force of attraction. %t has a negati&e sign.

(. Force o3 Re!6lsionBhen two charges repel each other the force is called force of repulsion. %t has a positi&e sign.

>. E:6i9$lent Resist$nceThe relati&e resistance that has e+ual &alue to the combined &alue of a resistor of a circuit is callede+ui&alent resistance. %t is denoted by 9(E).

-. Direct C6rrent"uch a current that does not change its direction is -nown as direct current. %t is denoted by 47, whichis obtained from primary and secondary cell.s

1 . Altern$tin4 C6rrent"uch a current that re&erses its direction with a constant fre+uency from positi&e to negati&e andnegati&e to positi&e direction is -nown as lternating 7urrent, obtained by generators. %t is denoted by

7.

11. Con9ention$l C6rrentn electric current considered to flow from points at positi&e terminal potential to points at negati&e

potential.

12. Prim$r# Cell &oltaic cell in which the chemical reaction that produces the e.m.f is not re&ersible is -nown as

Primary 7ell.

1 . Secon5$r# Celln electric cell that can be changed by passing an electric current through it is called "econdary 7ell.

The chemical reaction in this case is re&ersible.

1". F6se5 Pl64%t is a wired plug, which has its own cartilage fuse. %t is used in a ring main circuit.

1%. Electric Circ6it combination of electrical components that form a conducting path is called an electric circuit.

1&. Commerci$l Unit o3 Ener4# ,8 '/

1 -Bh is the energy produced by a resistor or conductor in 1 hour when it uses 1333 Batt power.


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1(. $tt%f 1 oule of electrical wor- is done in 1 second then the power is called 1 watt.

Electrost$tic In56ctionBhen a charged body brought close to another uncharged body then other body gains some chrgewithout any touch. This is called electrostatic induction.

ol5 *e$3 Electrosco!en electroscope is a de&ice that can be used for detection of charge.


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or8in4Bhen the plates of a capacitor are connected to a &oltage source. The electrons flow from a plate tothe positi&e charged terminal and * plate to negati&e terminal. Thus plate ac+uires + charge. 4ue toattraction &oltage on plates increases gradually. Then charging stops when the potential difference(&oltage) becomes the &oltage of source.

C$!$cit# or C$!$cit$nce%t is the ability of capacitor to store the charge. 7harge stored per unit &oltage is called capacitance.

UnitThe unit of capacitance is Darad coulomb>&olt.

F$r$5%f 1 coulomb charge charge produces a potential difference of 1 &olt then capacitance is e+ual to 1Darad.

F$ctors

7apacitance of a capacitor depends upon the following factors#S rea of PlatesS 8ature of dielectricS 4istance between platesS 8ature of metal platesS Temperature of 4ielectric and Plates

Electromoti9e Force ,e.m.3/ measure of the energy supplied by a source of electric current. %t is e+ual to the energy supplied by

the source to each unit of charge.e.m.3 Ener4# S6!!lie5 = C'$r4e

UnitThe unit of e.m.f is &olt.

Electric C6rrent$The rate of flow of charge is called electric current.$

)$t'em$tic$l Formccording to the definition#

Electric 7urrent 7harge >timeI :=t

UnitThe unit of current is mpere ( ) coulomb>sec

Am!ereBhen one coulomb charge passing through a conductor in one second the current is said to be 1

mpere.

Resist$nceDe3inition$The ratio of the potential difference across an electrical element to the current in it is called

resistance.$9esistance measures the opposition of the conductor to the flow of charge.

UnitThe unit of resistance is 5hm.

F$ctors on ?'ic' Resist$nce De!en5s9esistance 4epends upon the following factors#

Are$ o3 Cross Section o3 $ Con56ctor7 9esistance increases when area of cross section increases.*en4t' o3 Con56ctor7 9esistance increases when the length of conductor is increased.

Tem!er$t6re7 9esistance in metallic substances is directly proportional to temperature and in non


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metals is in&ersely proportional to the temperature.N$t6re o3 S6;st$nce7 9esistance also depends upon the nature of the conductor or substance.

O'mLs *$?St$tementThe current passing through a conductor is directly proportional to the potential difference across the

end points of the conductor.

)$t'em$tic$l Form

ccording to this law#

U % (U represents the sign of proportionality. 4o not write this in your e amination paper)

M IR Bhere 9 is a constant is called the resistance of the conductor.

ResistorThe body or thing that offers resistance in an electrical circuit is -nown as resistor. The appliance orde&ice that wor-s on the presence of electric current is -nown as resistor.

Com;in$tion o3 Resistors1. In SeriesBhen resistors are combined in series, they ha&e the following properties#S 7urrent passes through all resistors has e+ual &alue, i.e. % %1 %/S oltage is different according to the resistance.S Total &oltage is e+ual to the combined &oltage or the sum of the &oltages of all resistors, i.e. 1 O / O =S Total resistance is e+ual to the sum of all the resistances, i.e. 9E 91 O 9/ O 9=

Deri9$tion(4iagram)

s show in the abo&e diagram and according to the properties of combination.

O 1 O / O =

but %9 and 1 %91, / %9/ and = %9=, therefore#

%9(E) %91 O %9/ O %9=

%9(E) % (91 O 9/ O 9=)

R,E/ R1 R2 R

2. In P$r$llelBhen resistors are combined in parallel then this combination has the following properties#

S 7urrent has different ways to pass through.S 7urrent has different &alue in each resistor according to its resistance.S Total current is e+ual to the algebraic sum of each current, i.e.e % %1 O %/ O %=S Potential difference ( oltage) is same across each resistor, i.e. 1 / =S 9esistance is small or less than all combined resistance.S Total resistance is gi&en by the formula 1>9(E) 1>91 O 1>9/ O 1>9=

Deri9$tion(4iagram)

*y the help of properties of parallel combination#

% %1 O %/ O %=


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ccording to 5hm9 then we say that#

>9(E) >91 O >9/ O >9=

I >9(E) (1>91 O 1>9/ O 1>9=)

1=R,E/ 1=R1 1=R2 1=R

Di33erence ;et?een AC $n5 DCAltern$tin4 C6rrent

1. 7 is obtained by a resistor that is connected in series with a source of alternating current.2. %ts direction continuously changes.

. %t is obtained by a generator.". %ts transportation from one point to another point is &ery easy.%. %t has a fre+uency about A3 H' to C3 H'.&. 8o &oltage drop ta-es place in the time of transportation.

(. %t is not too dangerous.>. %t is cheaper than 47.-. %t changes &ery high to low or &ice &ersa.1 . %t changes its direction continuously as Oy and y.

Direct C6rrent

1. 47 is obtained by connecting the two ends of a conductor to the terminals of a batter.2. %ts direction remains unchanged.

. %t is obtained by a chemical reaction.". %ts transportation is &ery difficult.

%. %t has no fre+uency.&. :reat &oltage drop ta-es place in the time of transportation.(. %t is too dangerous.>. %t is e pensi&e.-. %t cannot change easily.1 . %t has no direction.

@o6leLs *$?"tatementS The heat produced by an electric current %, passing through a conductor of resistance 9 for time t is e+ual to %/9T. (/ represents power).

S The heat produced per unit time in a gi&en conductor is proportional to the s+uare of the current.

Deri9$tionccording to this law#

B U %/t (Here / represents the s+uare of current)

M I2Rt (Here / represents the s+uare of current)

Po?erThe rate of doing wor- is called Power.

)$t'em$tic$l Form

P B>T

I P %/9t>t

M P I2R

"ubstituting the &alue of % from 5hm9/N 9


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I P />9

I P /> >%

M P I

4ifference between 9esistance and 7onductanceResist$nce1. 9esistance is the measure of opposition by the conductor to the flow of charge.2. %t is the reciprocal of the conductance and is measured in &olt per ampere or ohm.

Con56ct$nce1. 7onductance of a wire is the ease with which current flows in it.2. %t is the ratio of current and potential difference. %ts unit is ampere per &olt or seimens.


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)A NETIS) AND E*ECTRO)A NETIS)

)$4netetals li-e iron, nic-el and steel attract each other magnetically. They are called magnets and always

point in a particular direction when suspended freely in the air.

Non+)$4netic S6;st$nces"ubstances that are neither attracted nor repelled by a magnet are called non magnetic substances.E amples are wood, glass and paper.

Ferrom$4netic S6;st$nces substance which beha&es li-e a magnet in the presence of a strong magnetic field is called a

ferromagnetic substance..

1. H$r5 Ferrom$4netic S6;st$ncesThe ferromagnetic substances which retain their magnetism when remo&ed from the magnetic field are-nown as hard ferromagnetic substances. E ample is steel.

2. So3t Ferrom$4netic S6;st$nceThe ferromagnetic substances which become magnets in the presence of a magnetic field and lose their magnetism when remo&ed from the magnetic field are -nown as soft ferromagnetic substance.E ample is soft iron.

)$4netic Fiel5The space surrounding a magnet in which its magnetic effect is f

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