Post on 02-Mar-2018
transcript
7/26/2019 Revision Exercise 2nd Term 2014
1/21
SECOND TERM PHYSICS REVISION EXERCISE
TOPIC : ELECTRISTATICS
1. (a) Q1= + 40 C 40cm Q= +!" C
!0 cm #0 cm
$%&' II
Q!= * "0 C
Figure II shows three point charges + 40 C, +36 C and -60 C are fixed at corners of a
Right-angled triangle. eter!ine the magnitudeand directionof the ',-a- ,c-%c
/cacts on charge "#$% the other two charges ( #)
7/26/2019 Revision Exercise 2nd Term 2014
2/21
(c) (i) Write an expression which shows the relationship between electric field, E and
electrical potential, V? (1)
222222222222222222222222222222222222222
(b)
V(Volt)
15
X (m)
-8 -6 - ! 5 "
-#5
$efer to the % & ' raph abo%e, setch a raph to show the %ariation of E with ' ? (4)
4. D
40 cm
A C
30 cm B 30 cm
- 80
C +45
C
*i+re
7/26/2019 Revision Exercise 2nd Term 2014
3/21
$efer to fi+re , point chare 1 - 8! . # +/5 . are placed at point 0
and . respecti%el2 03 3. ! cm, and 34 /! cm2 4etermine
(a) the electrical potentialat point 3 and 4 ? (3)
-
(b)Work doneto brin a chare of 65 . from point 4 to 3 ? (2)
777777777777777777777777777777777777772
(c ) 4etermine the res+ltant electric field acts on point 3
. (a) tate !a"##$# la%& (1)
(b) 9se :a+ss;s law to derive the electric field strength, Ethat is prod+ced
b a chared sphere with radi+s, $ as shown below (5)
+ +
+ +
+ + C'ared #p'ere
+ +
+ +
$efer to o+r e'pression of E, sketcha raph to show the variation of E
with distance, r . (3)
7/26/2019 Revision Exercise 2nd Term 2014
4/21
(c)
30o
0.5
0 small neati%e chared sphere with of mass 0.5 hans from a liht strin in an
electric field of intensit 800 *C-1prod+ced b a chared plate2
7/26/2019 Revision Exercise 2nd Term 2014
5/21
E= 20.0 V, r = 1.0
R= 6.0
R1= 4.0
E2 , r2=1.0
R2= 1.0
E1 , r1= 1.0
I= 1.0 A
I2=2.0 A
I1
a
b
c d
e
fX
Y
777777777777777777777777777777777777777
#2
A5 : (6) (%) 17V8 9V (%%) 1!V8 *1!V8 !V (b)
7/26/2019 Revision Exercise 2nd Term 2014
6/21
7.2 V
E
R
0.96 A
I
0.40 A
Determine
(a) t'e c"rrent , %'ic' lo%# t'ro"' t'e 10.0
resistor,
() e.m.
(c ) re#i#tance .
67,C CA7AC,6
12
.1 # 9
. 1# 9
.# / 9
7/26/2019 Revision Exercise 2nd Term 2014
7/21
20V d.c
2.0 !
0." !#.6 !
6 V
>hree capacitors are connected as shown in the abo%e fi+re2 4etermine
(a) the e+i%alent capacitance?
(b) the potential difference across 1# * capacitor?
(c ) the chare stored in each capacitor?
#2 (a) >hree initiall +nchared capacitors of capacitance #2! *, !25* and 26 *are connected to s #! V batter as shown in the fi+re below2
4etermine
7/26/2019 Revision Exercise 2nd Term 2014
8/21
(i) the effecti%e capacitance
(ii) the total chare s+pplied b the batter
(iii) the chare on the 26 * capacitor
(i%) the chare on the #2! * and on the !25 * capacitor
2 (a) 4efine capacitanceof a capacitor? (1)
(b) :plainwhat is the effect on electric field of a parallel plate capacitor when adielectricis inserted between the two plates of the capacitor2 ()
/tate al#othe effect of dielectric on the potential difffrence, V between the twoplates and the %al+e of the capacitance2 (#)
(c) (i) 4efine time constant, for charin circ+it of capacitor2 (1)
(ii) >he diaram below shows a circ+it +sed to chare a capacitor, . thro+h a hih
resistance $2
$ .
7/26/2019 Revision Exercise 2nd Term 2014
9/21
witch
e2m2f2 E
3 considerin the charin c+rrent, showthat the potential difference across
the capacitor at time t after the switch is closed is i%en b e+ation below
; < ( 1 = e
= t > C
) (4)
(d) etch a raph to show the %ariation of aainst t and %ariation of < aainst t
for two different re#i#tor o re#i#tance 1 and 2%'ere 1 ? 2 (4)
/2
5 @
Voltmeter
/ V 8 * ;
7/26/2019 Revision Exercise 2nd Term 2014
10/21
Aetalball witch
3at
>he fi+re shows a metal ball was held away from the batwhile closing the switch Sforsome instant +ntil the capacitor was fully charged
(a) (i) Drawa raph to show the variation of potential difference across thecapacitor with time?
V (Volt)
t( s)
-
(ii) Determine the initial currentflows in the circ+it at the moment the switch Sis closed?
(iii) 4etermine the time takenfor the capacitor to achie%e p.d. o 3 ;?
(b) 0fter the capacitor is f+ll chared, the switch is then opened and the metal ball isreleased toward the bat
(c)(i) Explainwhat will happen to the capacitorafter the metal ball maes
7/26/2019 Revision Exercise 2nd Term 2014
11/21
contact with the bat?
77777777777777777777777777777777777
777777777777777777777777777777777772
777777777777777777777777777777777777772
(ii) Drawa raph to show the variation of potential difference across the capacitor with time?
V (%olt)
t (s )
(iii) Calculate the time contactbetween the metal ball and the bat if the %oltmeter showin a readin of 12! V before the metal ball is bo+nded
bac?
52
1!2!V
#!!* 6!2!@
S
&o C.R.'
7/26/2019 Revision Exercise 2nd Term 2014
12/21
!2! @
>he abo%e circ+it shows circ+it with witch and a capacitor of capacitance #!! * whichma be chared b a batter of e2m2f2 1!2! V and neliible internal resistance connected
in series with a resistor of resistance !2! @, >he switch also enables the capacitor to
be dischare thro+h a resistor of resistance 6!2! @2 >he p2d2 V across the capacitor is
monitored +sin a s+itable cathode-ra oscilloscope (.2$2B2) to infinite resistance2
(a) (i) 4etermine the time constant for the charin of the capacitor?
(ii) 4etermine the time constant for the discharin of the capacitor?
(b) >he capacitor, initiall +nchared, is connected to the batter for time of 52! s andthen di#c'ared a "rt'er period o 5.0 # 2 At t < 10.0 # t'e capacitor i#aain c'ared or anot'er period o 5.0 #.
(i) 4etermine the p.d. acro## t'e capacitor at t < 5.0 # t < 10.0#and
t < 15.0 #.?
(ii) /ketc' on the same a'es, the appearance of the trace on the .2$2B or t'e15-#econd period&
;(olt)
7/26/2019 Revision Exercise 2nd Term 2014
13/21
0 5 10 15 t (#)
TOPIC : ELECTRIC C3RRENT
1(a) erive an expressionof the c"rrent ,in a piece of wire in termsof the cro##
#ectional area A, the drit elocit ;, the electron c'are eand the n"mer
o ree electron per "nit ol"me n&
2 (b) efinec"rrent den#it, @and then write down an expressionthat relates
c"rrent den#it @ to electrical cond"ctiit
and electrical ield
(c)!rite an expressionthat relates the drit elocit ;to electrical ield and
t'e mean time et%een colli#ion. ence ded"ce a orm"la or t'e
electrical cond"ctiit
in term# o n e
and t'e electron ma## m a#
ien elo%
< ne2
m
Explain the effect on electrical conductivit"of the metaland semiconductor
when the temperat+res of the materials increase?
67,C A!*,C 9,D
1 X
C cm
7/26/2019 Revision Exercise 2nd Term 2014
14/21
1!0
1#cm 50
$
= # cm
>he diaram shows a c+rrent of 1! 0 in a lon straiht %ertical wire X= and c+rrent of
50 flows in a rectan+lar coil C$2 >he coil has #! t+rn and dimensions C cm
and C 1# cm2 >he side C is placed parallel to X= and at a distance of # cm
from X=2
(a) 4etermine the manit+de and direction of the manetic force that acts on
(i ) wire C
(ii ) wire $
(b) E'plain whether the coil will rotate abo+t an a'is ?
777777777777777777777777777777777777777
7777777777777777777777777777777777777777
77777777777777777777777777777777777777722
7/26/2019 Revision Exercise 2nd Term 2014
15/21
7777777777777777777777777777777777777772
2E E E E E E E E E
X X X ; X X X X X X
X X X X X X X X X
X X X X X X X X X
X X X X X X X X X
X X X X X X X X X
>he abo%e diaram shows an electron mo%es with a +niform %elocit V which is
perpendic+lar to the manetic field in a %ac++m2 >he mo%in path of the electron is a circle
orbital of radi+s #2! miff the manetic fl+' densit is 52! ' 1!
-
> and its direction is pointinto the pageand the specific chare eDm of an electron is 12"6 ' 1!11.D2
(a) 4etermine(i) linear %elocit and an+lar %elocit of the electron2
(ii) period of orbit
(b) etch the mo%in path of the electron in the manetic field2(c) etch the direction of electric field E alon the mo%in path of the electron which
Will mae the electron mo%es in a straiht line
C2 >he fi+re shows a wire frame in the form of trianle
C$ carrin a c+rrent of 25 0 inside an +niform "!o
manetic field of fl+' densit 825 >2 3(i)4etermine the manit+de and direction of the manetic force acts on the sides 6!o 5!o
(a) C (b) C$ (c) $ $
(
7/26/2019 Revision Exercise 2nd Term 2014
16/21
J
KL
M
I
/2
he rod isfree to slide on the metal strips 03 and .42 0n +niform manetic field of fl+' densit
!26 > acts %erticall downwards and the %al+e of c+rrent flows into the rod is 825 0
(a) abel the entire forces act on the rod2
(b) .alc+late the res+ltant force acts on the rod2
(c) 4etermine the acceleration of the rod and itsdirection of mo%ement?
7/26/2019 Revision Exercise 2nd Term 2014
17/21
52 *i+re shows three parallel lon straiht riid wires
X, = and F carr the c+rrent of 1!0, 150 and #!02respecti%el 1!0 150 #!0
(a) 4etermine the res+ltant manetic field actson point C of wire = d+e to wire X and F? X = F
(b) 4etermine the force act on wire =
. 7
CA7 C6A!*,C ,*DFC,6*
1. (a) /tate t'e laws of electromagnetic induction& rod E E E E E
(9arada$# la% and enG$# la%) E E E E E() F#e t'e diaram ien elo% ded"ce E E E E E t'e expression of induced e.m.f, Ein term# E E E E E o manetic ield B lent' o t'e cond"ctor E E E E E and elocit o t'e cond"ctor ; & E E E E E (eer pae 8 H ) manetic ieldB
(c ) F#e t'e diaram ien elo%. derive an expression of induced e.m.f
7/26/2019 Revision Exercise 2nd Term 2014
18/21
, Ein t'e plane coil %it' * t"rn# and area A %'en it i# rotated in t'e "niorm manetic ield B a# elo%
< *BAW #in %t #ketch a graph E against t to #'o% t'e ariation o %it' t&
(eer pae 10 )
2. (a) /tate t'e meanin o I#el- ind"ctionJ and Im"t"al ind"ction I& ()
B "#in t'e principle# o #el-ind"ction and m"t"al ind"ction .eer tot'e aoe diaram derie an e:pre##ion o m"t"al ind"ctance a#
elo% < *1*2r2
67,C AC*A,*! CF*
1 0n ind+ctor with ind+ctance #5! mG is connected to a 02. s+ppl with pea
Voltae /! V and fre+enc 5! GH2 4etermine
(i) reactance of the ind+ctor
7/26/2019 Revision Exercise 2nd Term 2014
19/21
(ii) root mean s+are (r2m2s2) of the c+rrent flows in the ind+ctor
#2 0n alternatin %oltae V is represented b the followin e'pression
; < 230 /in 500t
7/26/2019 Revision Exercise 2nd Term 2014
20/21
(d) 4eri%e the e$uation representing instaneous powerin the capacitor and then
.alc+late the maximum instantaneouspo%erfor the capacitor?
1!2 (a) >he diaram below shows a 02. 2circ+it consists of a p+re ind+ctor of ind+ctance 2
, < ,o/in Wt
7"re ,nd"ctor
02.
witch
(a) +ppose the alternatin c+rrent, < flows in the circ+it at time t as the switch closed
is i%en b e+ationI , < ,o/in Wt
educethe e$uation of potential difference, %across the ind+ctor at time t when
7/26/2019 Revision Exercise 2nd Term 2014
21/21
the switch is closed2
(b) etch a raph of ( i) , aain#t t and (ii) ; aain#t t on the #ame a:i#and then
describe thephase differencebetween < and V?
(c) 4efine reactanceof t'e inductorand then ded+ce an e+ation of reactance E of
the ind+ctor in terms of fre$uenc", f and inductance, L.
(d ) 0n ind+ctor with ind+ctance #5! mG is connected to a 02. s+ppl with pea
Voltae /! V and fre+enc 5! GH2 4etermine
(i) reactance of the ind+ctor
(ii) root mean s+are (r2m2s2) of the c+rrent flows in the ind+ctor