Lab File Basics Of Electronics & Electrical Engg. (for PTU B.Tech. 1st year)

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NAME OF LAB: Basic Electrical & Electronics Engg.

CODE : ELE -103

Laboratory Manual

List of experiments:

1) To find voltage ,current relationship and power factor of a given R-L circuit

2) To connect three identical single phase transformer for three phase power

Transformation through following connection

Star-Star

Star-Delta

Delta- Star

Delta-star

3) To connect start and reverse the direction of rotation of three-phase induction motor

4) To find voltage ,phase voltage relationship ,line current, phase current relationship

incase of star –connected & delta connected ,3phase balanced Load circuit

5) To perform open circuit & short circuit tests of a single phase transformer

Also find the transformation ratio &efficiency

6) To perform the block rotor test of a three phase induction motor

7) To study the response of P-N Junction Diode

8) To study the transistor response

9) To analyze the truth tables of various basic digital gates.

10) To study the response of LVDT Transducer

11) To study various measuring instrument

1. Moving iron Instrument – a .Attraction type b. Repulsion type

2. Permanent magnet moving coil instrument

3. Dynamometer type instrument

Basic Electrical and Electronic Engg. - 1 -

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12) To study the use of multimeter.

13) To study the speed control of a dc shunt motor& to draw the speed variations

With respect to:

Field control

Armature control

EXPERIMENT NO. 1

AIM: To find voltage, current relationship and power factor of a given R-L circuit.

APPARATUS REQUIRED:

S.NO NAME OF

APPARATUS

RANGE QUANTITY

1. VATRIAC(Single

Phase)

0-260 V 1

2. Resistive load 0-10 A 1

3. Inductive load 0-10 A 1

4. AC voltmeter 0-300 V 1

5. AC Ammeter 0-10 A 1

6. Wattmeter(singlephase) 0-1 KW 1

7. DPIC main switch 32V 1

8. Connecting Leads ----- As per

requirement

THEORY: When only resistive load is connected with AC supply then the power factor

remainsUnity but when inductive load is connected with AC supply then the power factor

reduces,it can be ½ i.e. efficiency of single phase system reduces to 50% which effects our

electricity consumptionas well as AC Efficiency . But many stages RL series circuit is used


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for eg. Street light . So when a resistance and an inductor both are connected in series then

this type of circuit is called RL Series circuit and total resistance of both is called impedance.

And is denoted by Z and its units are Ohm.

So:-

Current flowing through an AC circuit is given as I=V/Z

Where V is the AC supply voltage and Z is the impedance of the circuit in ohms.

Power factor of an AC supply is given by cosΦ=P/VI

Where P is the power of the given load circuit in watts , V is the voltage applied to the circuit

in the

Volts and I is the current in amperes flowing through the circuit.

And the angle Φ is known as relation between V and I and its value can be calculated by

following

Formula:- Φ = (P/VI)

CIRUCIT DIAGRAM:


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PROCEDURE: Do as follows:

1. Make the connections of Variac, ammeter, wattmeter, voltmeter, load, as shown in circuit

diagram.

2. Connect this circuit to the main single phase supply.

3. Take the readings of ammeter, wattmeter, voltmeter for every 50V setting of Variac in the

Observation table as given below.

4. Note down 5-6 readings.

OBSERVATION AND CALCULATION:

S.NO. VOLTMETER

READING (V)

AMMETER

READING(I)

POWER(P)

WATTS

COSΦ=P/VI (P/VI)

1.

2.


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3.

4.

5.

6.

PRECAUTIONS:-1.Connections should be right & tight.

2.Always take accurate reading.

3.Meters used should be without error.

4.Be alert while doing practical.

RESULT:-

1.Current I increases directly in proportion to applied voltage V.

2.Power factor of the circuit is approx. same throughout for a given load.

EXPERIMENT NO. 2

AIM: To connect three identical single phase transformer for three phase power

transformation through following connections:

1. Star-Star

2. Star-Delta

3. Delta-Delta

4. Delta-Star

APPARATUS REQUIRED:

S.NO. NAME OF THE APPARATUS RANGE QUANTITY

1. Vatriac(3-phase) 0-460V 1

2. Single phase transformer 2KVA 3


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3. AC Voltmeter 0-500V 3

4. AC Ammeter 0-10A 3

5. TPIC main switch 32A 1

6. Connecting leads ------ As per reqiurement

THEORY:

When Star connections are done

Line voltage(VL)=√3 X Phase voltage(Vph)

Line current (IL)=Phase current(Iph)

When delta connections are done

Line voltage(VL)=Phase voltage (Vph)

Line Current(IL)=√3 X Phase current(Iph)

CIRUCIT DIAGRAM:


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First find primary & secondary windings of each transformer

Mark all transformer windings polarities by sequence test.

Connect all the three connections in following manner:


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1. Star-Star

2. Star-Delta

3. Delta-Delta

4. Delta-Star

Take the readings of voltmeter in the observation table as given below:

Note down at least one reading of each.


Connections S. No. Voltmeter

Reading(VL)

Voltmeter

Reading(Vph)

Ammeter

Reading(IL)

Ammeter

Reading(Iph)

Star-Star 1.

Star-Delta 2.

Delta-Delta 3.

Delta-Star 4.

PRECAUTIONS:

1. Connections should be right & tight.

2. Always take accurate reading.

3. Meters used should be without error.

4. Be alert while doing practical.


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RESULT:

When Star connection are done

Line voltage (VL)=√3 X Phase voltage(Vph)

Line current (IL)=Phase current (Iph)

When Delta connections are done

Line voltage (VL)=Phase voltage(Vph)

Line current (IL)= √3 X Phase current(Iph)

EXPERIMENT NO.3

AIM: To connect, start and reverse the direction of rotation of three-phase induction

Motor.

Apparatus required:

S.NO. Apparatus Required RANGE Quantity

1. 3 ph induction motor 5hp,415V 1


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2. Connecting Leads ----- As per

requiremet

3. DOL Starter 1

4. TPIC main switch 32 Amp 1

5. AC voltmeter 0-500V 1

6. AC Ammeter 0-20Amp 1

Theory:

When motor is connected to a three-phase supply through a DOL Starter (Direct Online

Starter) or a Star delta Starter, then the motor should run in anticlock wise direction

but/Many times motor runs clockwise. So, it is desired to change its DOL. So, for the same

wehave to interchange any two supply terminal of the motor to make its direction anti-

clockwise.The starter’s main function is to protect the motor from overload condition and it

also provides easy ON-OFF the motor so it is necessary to use a starter. In this practical we

have used a DOL starter,which runs a three-phase 3hp motor.Whose circuit diagram is as

shown.

CIRCUIT DIAGRAM:


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1. Make the connections as per circuit diagram-1

2. Now switch on the power supply.

3. The direction of rotation (DOR) should be noted when motors starts.

4. Now if the direction is clockwise or it is required to change the direction of rotation of

motor then the interchange any two phases as shown in diagram-3.

5. Now note the new DOR of motor.

6. Now direction of rotation of the motor is reversed by changing any two phase

terminal.

OBSERVATIONS & CALCULATIONS


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S.NO. IN FIRST STAGE IN SECOND STAGE

CONNECTIONS DOR CONNECTIONS DOR

1.

2.

3.

4.

PRECAUTIONS:

1. Make the connections as per circuit diagram.


3. Note the direction of rotation carefully.

4. Do every procedure carefully.

RESULT: Now we have come to know how to change the DOR of any three phase

induction motor by interchanging any two supply terminals.

EXPERIMENT NO. 4


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AIM: To find the line voltage, phase voltage relationship,line current,phase current

relationship in case of star – connected & delta connected,3-phase balanced load

circuit.

APPPARTUS REQUIRED

S.NO. NAME OF

APPARATUS

RANGE QUANTITY


2. 3-phase Balanced

Resistive load

0-10A 1


4. AC Ammeter 0-10A 3


6. Connecting leads ------ As per

requirement

THEORY:


Line voltage (VL)=√3 X Phase voltage (Vph)

Line current (IL)=Phase current(Iph)



Line current(IL)=√3 X Phase current (Iph)


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CIRCUIT DIAGRAM:


1. Make the connections of variac, ammeter, wattmeter and voltmeter & 3 –ph load, as shown

in diagram.

2. Connect this circuit to the main single phase supply.

3. Take the reading of ammeter,wattmeter and voltmeter in the observation table as given

below.

4. Note down 3-4 readings.


Connections S.No. Voltmeter

Reading(VL)

Voltmeter

reading(Vph)

Ammeter

reading

(IL)

Ammeter

reading(Iph)


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STAR

1.

2.

3.

4.

DELTA

1.

2.

3.

4.

PRECAUTIONS:





5. Always avoid short circuit & loose connection.

6. Never exceed the permissible value of current , Voltage and power of any instruments.

7. Check all the connections before switch on the power supply.

RESULT:


Line voltage (VL)=√3 X Phase voltage (Vph)


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Line current(IL)=Phase current(Iph)



Line current(IL)=√3 X Phase current (Iph)

EXPERIMENT NO. 5

AIM: To perform open circuit & short circuit tests of a single phase transformer. Also

find the transformation ratio & efficiency.

A.FOR OPEN CIRCUIT TEST:


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APPARATUS REQUIRED:

S.NO. NAME OF APPARATUS RANGE QUANTITY


2. 1-Phase transformer 2kv A 1


4. Wattmeter 0-

1000W

1

5. AC Ammeter 0-1 A 3

6. DPIC main switch 32 A 1

7. Connecting leads ------- As per

requirement

THEORY:

When open circuit test is performed, the secondary side of the transformeris on no

load.The primary is supplied at its rated voltage, since there is no current in the secondary, a

very small current flows through primary. So copper loses are negligible &the wattmeter

gives only iron loses.

CIRCUIT DIAGRAM:


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1. Make the connections of variac ,ammeter,voltmeter&a single-phase transformer

as shown in circuit diagram.

2. Set the Variac to zero position.

3. Switch on the power supply.

4. Increase the variac voltage till rated primary voltage is reached.

5. Take the reading of ammeter,wattmeter,voltmeter in the observation table as given

below.

6. Now find transformation ratio.

7. Also find efficiency of transformer.

OBSERVATION AND CALCULATION

S.No. Primary side Secondary Transformation


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Side Ratio,

K=Vs/VpVoltage

Vp

Current

Io

Power

Wi

Voltage

Vs

1.

2.

3.

4.

5.

6.

7.

PRECAUTIONS:

1. Connections should be right &tight.




RESULT:

In open circuit test we find iron loses.

B.FOR SHORT CIRCUIT TEST:

APPARATUS REQUIRED:


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S.NO. NAME OF APPARATUS RANGE QUANTITY1. Vatriac(3-phase) 0-270V 12. 1-phase transformer 2kv A 13. AC voltmeter 0-300 V 14. Wattmeter 0-1000W 15. AC Ammeter 0-10a 26. DPIC main switch 32A 17. Connecting leads ------ As per requirement

THEORY:

When short circuit test is performed , the secondary side of the transformer is short circuited. The primary is supplied at very less voltage, since there is heavy current in the secondary, a very large current flows through primary .so copper loses occurs & the wattmeter gives only copper loses.

CIRCUIT DIAGRAM:


1. Make the connections of variac ,ammeters,voltmeter and a single phase transformer,as shown in circuit diagram.

2. Set the variac to zero position.


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3. Switch on the power supply.

4. Increase the variac voltage till rated secondary current is reached.

5. Take the readings of ammeter,voltmeter, wattmeter, in the observation table as given below.

6. Now find efficiency of transformer.


S.NO. Primary side Secondary side Current

VoltageVsc

Current Isc

Power Wcu

1.2.3.4.5.6.7.

PRECAUTIONS:

1. Connection should be right & tight.




RESULT: In short circuit test we find copper losses.

EXPERIMENT NO.6

AIM: To perform the block rotor test of a three phase induction motor.

APPARATUS REQUIRED:


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S.NO. NAME OF

APPARATUS

RANGE QUANTITY


2. Three phase induction

motor

3HP 1

3. AC voltmeter 0-500 V 1

4. AC ammeter 0-10A 1

5. Wattmeters 0-1000W 2

6. Break load 0-50 kg 1


8. Connecting Leads ------ As per

requirement

THEORY:

There are generally two types of tests which we perform on a three phase induction

motor.


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1. No load test

This test is generally performed for measuring iron loses. In this case

Total power input at no load (Po)=(W1-W2)watts

Copper losses =3 to R watts

Total Constant losses (Pc)=Po-3 to R watts

2. Block rotor test

This test is generally perform for measuring copper losses.In this case

Total power input at break load,(Psc)=(W1+W2)Watts

In case of block rotor,(Psc)=Pcu

Input =Output+Po+Pcu

And efficiency is given by:

Efficiency(η%)=Output x 100/Input

Here W1 & W2 are wattmeters readings: Both the wattmeter find looses in the

Motor . Where as one wattmeter is find cooper looses and another one is find iron

Looses in the three phase induction motor.

CIRCUIT DIAGRAM:


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S.No. Wattmeter Readings

W1 W2

Line

Voltage

V

Line

Current

I

Total power

W=W1+W2

1.

2.

3.

PROCEDURE:Do as follows:

1. Make the Connections as per circuit diagram.

2. Now block the rotor by tightening the belt so that rotor shouldn’t move.

3. Keep the variac at its minimum value.

4. Switch on the AC input to both the power supplies.

5. Now increase the applied voltage graduately with the of variac until full load current flows

through the motor.


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6. Record the reading of wattmeter,ammeter and voltmeter observation table&calculate the

power and efficiency.

7. take 3-4 reading and record the reading of wattmeter ,ammeter&ion voltmeter reading in

observation table and calculate the power and efficiency.

PRECAUTIONS:

1. Connections should be tight and right.


3. Meter used should be without error.


5. Always start from zero voltage.

6. Belt should be so tight so that rotor should not move.

RESULT:

In this experiment we are find the efficiency of the three phase induction motor.

EXPERIMENT NO.7


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AIM:To Study the response of P-N Junction Diode.

APPARATUS REQUIRED:

S.NO. NAME OF

APPARATUS

RANGE QUANTITY

1. Diode Silicon

Germanium

1 each

2. Voltmeters 0- V

0- V

1 each

3. Ammeters 0- mA

0- μA

1 each

4. Resistance

5. Power supply 0- V

0- V

1 each

6. Connecting leads -------- As per

requirement

THEORY:

A p-n junction diode can be realized when a p-type crystals brought in contact with

a n-type crystal structure remains constant.The region around p-n junction is devoid of free

charge carriers.This is known as depletion layer.The act of applying voltage across P-N

junction is known as biasing.There are two ways in which a junction can be biased , one is

forward biased and second is reversed biased.The +ve terminal of the battery is connected to

p side of the junction and –ve to n side.In this set up the conduction across p-n junction

takes place due to migration of majority carriers.

PARAMETERS OF DIODE:


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1 KNEE VOLTAGE: It is forward voltage at which the current flowing through the diode

suddenly reaches higher value.

2 REVERSE BREAKDOWN VOLTAGE: The minimum reverse voltage at which the

avalanche breakdown of the p-n junction diode is occurring.

3 IDEAL DIODE: Ideal diode have barrier potential zero.

4 ZENER DIODE: It acts as a voltage regulator.

CIRCUIT DIAGRAM:

PROCEDURE:

1. Connect the circuit as shown in circuit diagram no.1

2. Bring the variable voltage to the DC source to zero.The current millimeter will also be

zero.

3. Increase the variable voltage DC supply source slowly and in steps.

4. Don’t exceed the current rating of the diode.This completes the observation of V-I

characteristics of forward biased diode.

5. Draw the graph for this.

6. Repeat the steps2,3 and draw the graph.

CIRCUIT DIAGRAM:


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OBSERVATION & CALCULATIONS

S

.

N

O

.

SILICONDIODE GERMANIUM DIODE

FORWARD

CHARACTERISTCS

REVERSE

CHARACTERISTCS

FORWARD

CHARACTERISTCS

REVERSE

CHARACTERISTCS

If Vf Ir Vr If Vf Ir Vr

1

.

2

.

3

.


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4

.

5

.

PRECAUTIONS:

1.All the connections should be tight.

2.The value of the current should be increased slowly.

RESULT:

In this experiment we find the forward & reverse characteristics of the diode.

EXPERIMENT NO. 8


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AIM:To study the transistor response

APPARATUS REQUIRED

S.NO. NAME OF

APPARATUS

RANGE QUANTITY

1. Experiment kit NPN

transistor

1

2 Transistor NPN 1

3. RESISTOR 100Ω,0.5W 1

4. DC AMMETER 0 - A

0 - A

1 each

5. DC VOLTMETER 0 – 1.5V

0 - 10V

1 each

6. Connecting Leads ------- As per

requirement

THEORY:

Transistor is a three semiconducting layers,two junction device,which is used for

weak signal’s amplication .The input is connected in forward biased,whereas the output

junction is reversed biased.

When we draw the curve between collector current and collector emitter voltage with

respect to Ib then following threenregions appear;

(1)Saturation region:


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When Vce increases,IC increases from zero to near saturation value of Ib .When Vce is

reduced ,Ic doesnot reduced.In this region input as well as junctions are forward biased .

(2)Active region:

When Vce is increased further output junction is reversed biased . the transistor operates in

active region and Ic increases Vce fiased . the transistor operates in active region and Ic

increases Vce for constant value of Ib.In this region the input junction is forward biased and

output junction is reversed biased.The value of Ic can be changed by changing the value of

Ib.

(3)Cutoff region:

Whwn Ib =0,still some Ic =Iceo flows in the collector region.this is independent of Ib or Vce.

In this region both the junctions are reversed biased.

TRANSISTORS CHARACTERISTICS

INPUT CHARACTERISTICS:

In common base configuration, the curve plotted b/w the emitter current Ie and the emitter

base voltage Veb.At constant collector-base voltage Veb,is called input characteristics. Then

input dynamics resistance:

Ri=∆Veb at constant Veb

∆ Ie

OUTPUT CHARACTERISTICS

In common base configuration ,the curve plotted b/w the collector current Ic and the

collector base voltage Vcb ,at constant emitter current Ie is called Output characteristics.


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Then output dynamic resistance:

Ro=∆Vcb at constant Ie

∆Ic

For both the characteristics,we may determine dc and ac current amplification factor:

αac = ∆Ic at constant Vcb

∆Ie

αde = Ic at constant Vcb

Ie

CIRCUIT DIAGRAM:

OUTPUT CHARACTERISTICS:

In common base configuration,the curve plotted b/w collector current Ic and the

collector base voltage Vcb ,at constant emitter current Ie is called is output characteristic then

output dynamic resistance:


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Ro = ∆ Vcb at constant Ie

∆Ic

I or both the characteristics,may determine dc and ac current amplification factor:

α ae = ∆Ic at constant Vcb

∆Ie

αdc = Ic at constant Vcb

Ie

PROCEDURE:

1. Make the connections as per circuit diagram.

2. Set both the power supplies at zero.

3. Switch on the AC input to both the power supplies.

4. For input characteristics fix end voltage Vcb=5V

5. Now increase the Veb voltage in steps of 0.05 V and note down the corresponding

value of emmiter current Ie and record them in the observation table.

6. Draw the input characteristics taking Veb on X axis and Ie on Y axis.

7. Repeat the steps for Vcb=10 V.

8. For output,fix Ie = mA ie , keeps the input circuit open.Change the collector base

voltage Vcb in steps and note down the corresponding values of Ic in observation table.

9. Draw the output characteristics taking Vcb on X axis and Ic on Y axis.


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A. FOR INPUT CHARACTERISTICS

Characteristics S.NO. Vcb=5V Vcb=10V

Voltmeter

Reading

(Veb)volts

Ammetr

Reading

(Ie)mA

Voltmeter

Reading

(Veb)Volts

Ammeter

Reading

(Ie)mA

For input

1.

2.

3.

4.

B.FOR OUTPUT CHARACTERISTICS

Characteristis S.No. Ie=0 mA

Ie=2mA

Ie=4mA

Voltmeter Ammeter Voltmeter Ammeter Vcb Ic


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Reading

(Vcb)volts

Reading

(Ic)mA

Reading

(Veb)Volts

Reading

(Ie)mA

Volts

mA

For output

1.

2.

3.

4.

PRECAUTIONS:

1. Connections should be right and tight.




RESULT:

In this experiment we find the input & output characteristics of the trans

EXPERIMENT NO. 9

AIM: To analyse the truth tables of various basic digital gates.

Apparatus required:


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S.NO. APPARATUS

REQUIRED

RANGE QUANTITY

1. DC power supply 5V 1

2. Various digital

IC’s

a)OR Gate

b)AND Gate

c)NOT Gate

d)NAND Gate

e)NOR Gate

7432

7408

7404

7400

7402

1

1

1

1

1

3. Connecting leads As per

requirement

4. LED 5

THEORY:

All types of logic gates deals with binary.The binary information is a combination

of binary variables.For this purpose logic circuits which are called gates are used.These gates

are the fundamental building blocks of any digital system.

The important points regarding these gates are:

1.Each logic gate has its own symbol

1.OR GATE

2.AND GATE


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3.NOT GATE

4.NAND GATE

5.NOR GATE

PROCEDURE:

Do as follows:

a)FOR OR GATE

1. Make the connections as per circuit diagram and connection diagram.

2.Connect the gates,switches A,B,&C and LED with supply (+5V) to 14 no. Pin and pin no. 7

to ground.

3.Now switch on A,B,C in sequence and note down the state of LED in truth table as given

in observation and calculations.

b)FOR AND GATE



to ground.



c)FOR NOT GATE



to ground.




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d)FOR NAND GATE



to ground.



5)FOR NOR GATE



to ground.

3. Now switch on A,B,C in sequence and note down the state of LED in truth table as given


OBSERVATION & CALCULATIONS:

1.OR GATE

TRUTH TABLE

S.NO.

A B C Y=A+B+C


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1. 0 0 0 1

2. 1 0 0 1

3. 0 1 0 1

4. 0 0 1 1

5. 1 1 0 1

6. 1 0 1 1

7. 0 1 1 1

8. 1 1 1 1

9.

2.FOR AND GATE

TRUTH TABLE

S.NO. A B C Y=A*B*C

1.

2.

3.


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4.

5.

6.

7.

8.

9.

3. FOR NOT GATE

S.NO. A Y=A

1.

2.

4.FOR NAND GATE TRUTH TABLE

S.NO. A B C Y=A*B*C X=Y

1.

2.

3.

4.

5.


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6.

7.

5) FOR NOR GATE

TRUTH TABLE

S.NO. A B C Y=A+B+C X=Y

1.

2.

3.

4.

5.

6.

PRECAUTIONS:

1. Always give positive supply to pin no.14 and ground pin no.7 of any logic gate.

2. Connectivity should be right and tight.

3. Truth table should be accurate.

4. Supply should not be greater than regulated +5V.


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EXPERIMENT NO. 10

AIM: To study the response of LVDT Transducer

Apparatus required:

1. LVDT kit

2. Connecting Leads

3. Multimeter

THEORY:


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LVDT is also known as Linear Variable differential transducer, which is use to

measure displacement fo core. The output voltages of LVDT is a function of core

position. The basic principal behind it is Electro magnetic induction. When the core is

at centre, the rate of change of flux linkages with the windings s-1 and s-2 are the

same. Therefore, the induced EMF in the both windings is of same magnitude and

output is 0 as S-1 &S-2are cross connected. When the position of the core is changed,

different EMF are induced in two windings.And resultant voltage appears across the

output terminals.

CIRCUIT DIAGRAM

PROCEDURE Do as follows

1 Make the connections as per circuit diagram.

2 Connect the instrument such as auto transformer on the primary and voltmeter at

the output are connected

3Now switch on the power supply.

4Give the rated voltage to the primary of the LVDT.

5Now change the core position and record the output.

OBSERVATION & CALCULATIONS


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Sr. No. Output Voltage

Forward Reverse

Displacement

Forward Reverse

1.

2.

3.

4.

5.

PRECAUTIONS:


2. Observation should be accurate.

RESULT: The curve for displacement (on X-axis) v/s ( On Y- axis) is similar to the

theoretical one


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EXPERIMENT NO. 11

AIM: To study various measuring instruments

1. Moving iron instruments-(a) Attraction type (b)Repulsion type

2. Permanent Magnet moving coil instruments

3. Dynamometer type instruments

APPRATUS REQUIRED:

Sr. no. Apparatus required Quantity1. Moving iron instruments

Attraction type- AC voltmeter& ammeterRepulsion type- AC voltmeter& ammeter

1 each

2. Permanent Magnet moving coil instrumentsDC voltmeter& ammeter

1 each

3. Dynamometer type instruments 1 each


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THEORY:

PERMANENT MAGNET TYPE MOVING COIL INSTRUMENT-

These instrument are very sensitive and accurate. These instruments can be used only on d.c.

as voltmeter and ammeter. The pictorial view is shown The basic principle of permanent type moving coil instrument is that when a current carrying conductor is placed in a magnetic field, a mechanical force is exerted on the conductor. The simple view of permanent magnet type moving coil instrument is shown as in fig. In this case a deflecting coil is placed in a strong magnetic field is produced by permanent magnet when current flows through the coil, a force is exerted & deflection take place. The controlling torque is provided with the help of spiral spring where as deflecting torque is provided with the help of eddy currents as the coil is placed over the aluminum former. This instrument can be used for DC measurement only. Its scale is uniform.

MOVING COIL INSTRUMENT

It consists of a powerful permanent shoe magnet. A coil of many turns of fine wire wound on a light aluminium former. An iron core is inserted in between the coil sides to reduce reluctance for magnetic lines of forces. The coil is mounted on the spindle and acts as moving element. Two phosphorous bronze spiral hair springs are attached to the spindle. The spring


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provide the controlling torque as well as they act as incoming and outgoing leads for the current. Eddy current damping is provided by the aluminium former. When the instrument is connected in the circuit, the operating current flows through the coil which is mounted on the spindle. Since the coil is placed in the strong field of permanent magnets, a force is exerted on the current carrying conductors of the coil which produces deflecting torque. Thus the pointer attached to the spindle in deflected over the calibrated scale. If the direction of current is reversed the direction of deflecting torque is also reversed as field produce by permanent

magnet does not change.

DYNAMOMETER TYPE INSTUMENT:

It consists of two coils, one is called moving coil & other one is called fixed coil. The fixed coil produces main magnitude field, in which moving coil is placed when current flows through these coils, a force is exerted & deflection take place in moving coil because when current carrying conductor is placed in the magnetic field, experiences force. The controlling torque is provided with the help of spiral spring where as deflecting torque is provided with the help of air friction. This instruments is costly because special techniques is used for manufacturing these type of instruments.

PRECAUTIONS:

1. Study the instruments dial carefully.

2. Don’t touch pointer & spiral spring.

3. Remove every part carefully.

EXPERIMENT NO. 12

AIM: To study the use of multimeter


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APPRATUS

Sr.no. Name of Apparatus Range Quantity1. Digital multimeter ------- 12. Connecting leads ------- As per requirement

Theory: A multimeter is basically a permanent magnet moving galvanometer. There is an iron core pivoted on two jeweled bearings. The coil is wounded on an aluminium former which is free to rotate in the field of permanent magnet. An aluminium pointer is attached to the coil and it moves over the gradual scale. There are two spiral springs providing path to current as well as restoring torque. It can measure voltage, current and resistance for which its galvanometer is converted to voltmeter, ammeter and ohmmeter with the help of suitable circuit incorporated in it.There are basically two types of multimeter

1. Digital multimeter

2. Analog multimeter

DIGITAL MULTIMETER- It display the a.c. or d.c. voltages being measured as discrete numerals in the decimal number system. It limits observational errors. Its use increase the speed with which readings are taken.


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2. ANALOG MULTIMETER- It gives the reading by deflecting its needle. In it chances of occurring error are more as reading is to be taken from deflecting needle. The

pictorial view of analog multimeter as shown below-

Above all DMM is better than AMM, as it display the reading in digits therefore chances of error occurring are very less.


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EXPERIMENT 13

AIM: To study the speed control of a dc shunt motor & to draw the speed variation with respect to

1. Field Control2. Armature Control

APPARATUS REQUIRED :

S.No. Name of Apparatus Range Quantity

1. DC SHUNT MOTOR 5 HP, 220V 1

2. DC VOLTMETER 0-300V 1

3. DC AMMETER 0-10A 1

4. RHEOSTATC 0-1500Ω, .75A 1

5. CONNECTING LEADS ---- AS PER REQUIREMENT

6. RHEOSTATE 0-20Ω, 16A 1

7. DPIC MAIN SWITCH 32A 1

8. TACHOMETER ---- 1

THEORY

A DC shunt motor consist of two parts, one movable & other static. The movable part is called ARMATURE & static is called filed. Field winding is connected in parallel with armature & it has very high resistance as compared to armature.

The speed of shunt motor can be calculated with following relation:

N = k = k

Hence the speed either changing the shunt fie motor can be changed by either changing the shunt field current ish by inserting an external resistance in field circuit or by changing the back emf, Eb by inserting an external resistance in armature circuit.

i.e V-laRa


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CIRCUIT DIAGRAM:

Armature Control

FIELD CONTROl


1. Make the connections as per circuit diagram.2. Set the rheostat at zero position.3. Switch on the DC power supply.


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4. Now change the rheostat of filed & corresponding note down RPMs & field current.5. Take 5-6 readings and note in the observation table.6. Similarly vary the armature resistance & correspondingly note down in observation

table as given below:

OBSERVATION:

S. NO. CONTROL FIELD CURRENT ISH

RPM N

FIELD 1.1A

1 0.85 A

2 0.725 A

3 0.625 A

4 0.625 A

5 0.575 A

ARMATURE BACK EMF EB RPM N

1 220 V 1500 RPM

2 200 V 1400 RPM

3 180 V 1300 RPM

4 160 V 1200 RPM

5 150 V 1100 RPM

PRECAUTIONS:

1. The current, voltage should be in limit.2. Do not touch any live wire.3. Connections should be write & tight.


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RESULTS

1. By increasing resistance of the field current decreases, thus speed increases.2. By increasing resistance of the armature voltage drop in armature increases, thus back

emf Eb decreases, thus speed decreases.


Date post:	18-Nov-2014
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Lab File Basics Of Electronics & Electrical Engg. (for PTU B.Tech. 1st year)

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