Measuring Systems And Instrumentation

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Q1:- The pressure coil of a single phase Energy meter is wound on

       1.       One limb of the laminated core

       2.       Both the limbs of the laminated core with different turns

       3.       Both the limbs of the laminated core with same number of turns

      4.       The centre of the limbs of the laminated one same number of turns

ANSWER:-4

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Q2:- If the megger terminals are connected to 230 v supply , megger will

        1.       Work

        2.       Not work

        3.       Burn

        4.       Partially damage

ANSWER:-3

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Q3:- Multimeter can be used for measuring

       1.       Alternating current quantities

       2.       Dc quantities

       3.       Ac and dc quantities both

       4.       Pulsating dc quantities

ANSWER:-3

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Q4:- The meter of multimeter will work on

1.       Dc supply

2.       Ac supply

3.       As and dc both

4.       Half wave rectifier

ANSWER:-1

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Q5:- Speed of the megger is kept at

        1.       100 rpm

        2.       120 rpm

        3.       140 rpm

       4.       160rpm

ANSWER:-4

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D.C. Machine

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Q1:- The emf of a dc generator depends on

1.       Commutation

2.       Speed

3.       Frequency

4.       Brush contact drop

ANSWER:-2

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Q2:- The function of the starter in a dc machines is

1.       To avoid the excessive current at starting

2.       To control the speed

3.       To avoid armature reaction

4.       To avoid excess heating

ANSWER:-1

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Q3:- An external resistance added in the field of a dc shunt generator will

1.       Increase the speed of the generator

2.       Increase the voltage of the generator

3.       Decrease the voltage of the generator

4.       Increase the power delivered

ANSWER:-3

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Q4:- The speed of a D.C. shunt motor is required to be more than F.L. speed. This is possible by

1.       Increasing the armature current

2.       Decreasing the armature current

3.       Increasing the excitation current

4.       Reducing the field current

ANSWER:-4

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Q5:- An emf is induced in the windings of an armature of a dc generator when the armature rotates in

1.       Alternating magnetic flux

2.       Magnetic field

3.       Electrostatic field

4.       Electromagnetic flux

ANSWER:-2

Measuring Systems And Instrumentation

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Q1:- If the battery of the multimeter is weak it will give 

1. accurate reading
2. more reading
3. less reading
4. no reading

ANSWER:-3

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Q2:- The three advantage of moving iron instruments are

1. high sensitivity uniform scale and robust construction 
2. uniform scale robust construction and relatively cheap
3. high sensitivity uniform scale and relatively cheap
4. robust construction relatively cheap and use able for ac and dc\

ANSWER:-4

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Q3:- The meter used measuring potential difference of a circuit is called 

1. voltmeter
2. ammeter
3. energy meter
4. ohm meter

ANSWER:-1

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Q4:- The most essential instrument required by a T.V. technician is

1. voltmeter
2. megger
3. ohm meter
4. avometer

ANSWER:-4

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Q5:- The name plate of a single phase energy meter genrally provides.

1. meter constant 
2. voltage and frequency 
3. current
4. all of the above three

ANSWER:-4

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Measuring Systems And Instrumentation

Q1:-The megger voltage for testing 250 v installation should be

1.       1000 v

2.       500 v

3.       300 v

4.       100 v

ANSWER:-2

D.C. Machine

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Q1:- The dummy coil in dc machine is used to

1.       Elimination reactance voltage

2.       Elimination armature reaction

3.       Bring about mechanical balance of armature

4.       Elimination harmonics developed in the machine

ANSWER:-3

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Q2:- The current flowing in the conductors of a dc motor is

1.       Ac

2.       Dc

3.       Ac as well as dc

4.       Transients

ANSWER:-1

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Q3:- As the load is increased the speed of a dc shunt motor will

1.       Remain constant

2.       Increase proportionately

3.       Increase slightly

4.       Reduce slightly

ANSWER:-4

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Q4:- One dc motor drives another dc motor .The second motor when and driven.It 

1. runs
2. does not run as generator
3. runs as a geneator
4. also runs as a motor

ANSWER:-3

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Q5:- In any dc generator the emf generated in the armature is maximum when

1.       Rate of change3 of flux inked is minimum.

2.       Rate of change of flux inked is maximum.

3.       Flux linked with conductor is maximum

4.       Flux linked with conductor is minimum

ANSWER:-2

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Indction Motor's Questions

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Q1:- The speed of the rotor field of an induction motor

     1.       is equal to synchronous speed

     2.       is equal to motor speed

     3.       is equal to zero

     4.       none of the above

ANSWER:-1

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Q2:- If the full load speed of a 4 pole 3-phase induction motor is 1440 rpm its speed at half load will be

     1.       1460 rpm

     2.       1440 rpm

     3.       1400 rpm

     4.       1000 rpm

ANSWER:-1

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Q3:- If the rotor terminals of a 3-phse slip ring induction motor are not short circuited and the supply is given to the stator the motor will

     1.       Not start

     2.       Start running

     3.       Run at high speed

     4.       Run at low speed

ANSWER:-1

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Q4:-Generally a 3-phase slipring induction motor is started with

1.       D.O.L. starter

2.       Star delta starter

3.       Auto transformer starter

4.       Stator rotor starter

ANSWER:-4

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Q5:- The speed of the squirrel cage induction motor can be controlled from

1.       Stator side

2.       Rotor side

3.       Stator and rotor sides both

4.       Supply voltage side

ANSWER:-1

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DC machine Questions

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Q1:- A simple method of increasing the voltage of and dc generator is

1.       To decrease the air gap flux density

2.       To increase the speed of rotation

3.       To decrease the speed of rotation

4.       To increase the length of the armature

ANSWER:-2

Q2:- An external resistance is added in the series with the field of a dc shunt motor .When the motor runs the effect of resistance is

1.       To reduce the speed of the motor

2.       To increase the speed of the motor

3.       To reduce the armature current drawn by the motor

4.       To reduce the losses

ANSWER:-2

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Q3:- If the speed of dc generator is increased the generated emf

1.       Increases

2.       Decreases

3.       Remains constant

4.       First decreases and then increases

ANSWER:-1

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Q4:- If the speed of a shunt motor increases the back emf

1.       Increases

2.       Decreases

3.       Remains constant

4.       First decreases and the increases

ANSWER:-1

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Q5:- The function of a commutator in dc generator is

1.       To collect current from conductor

2.       To change dc to ac

3.       To conductor the current to the brushes

4.       To change ac to dc

ANSWER:-4

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Electrical Instruments and measurements

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Q1:- The dynamometer type wattmeter is used on

       1.       ac only

       2.       dc only

       3.       ac and dc both

      4.       full wave rectified

ANSWER:-3

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Q2:- Most commonly used wattmeter is

       1.       induction type

       2.       electrostatic type

       3.       dynamometer type

       4.       moving iron type

ANSWER:-3

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Q3:- A wattmeter can be used

   

       1.       only for one rated current

       2.       for different rating current without any change

       3.       different rating current with change of connection without multimeter

      4.       with different currents with change of connections and multimeter

ANSWER:-4

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Q4:- The meter constant of energy meter is given by

       1.       rev./kw

       2.       rev./kWh

       3.       rev./watt

       4.       rev./kWhr

ANSWER:-2

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Q5:- Wattmeter are available for different rating of

     

       1.    current

       2.    voltages

       3.       currents and voltages both 

       4.       currents and voltages with change of connection without multiplier

ANSWER:-4

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UPRVNL Questions

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Q1:- For constant power o/p the current drawn by a synchronous motor will be minimum when the p.f. is

1. lagging
2. zero
3. unity
4. leading

ANSWER:-3

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Q2:- Final value theorem is used to determine

1. steady state value of the system o/p
2. initial value and transient behaviour both
3. initial value of the system o/p
4. none of the above

ANSWER:-1

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Q3:- The convolution of a finite sequence with an infinite sequence 

1. may be a finite or finite sequence 
2. is always an infinite sequence
3. cannot be found
4. is always a finite sequence

ANSWER:-2

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Q4:- The band width of signal x(t) is 10 kHz then the band width of signal x(2t) will be 

1. 2 kHz
2. 5 kHz
3. 20 kHz
4. 10 kHz

ANSWER:-3

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Q5:- In respect of class D type chopper which of the following statement is correct

1. the load voltage is always positive and load current may either positive or negative
2. the load voltage is always positive and load voltage may either positive or negative
3. the load current is always negative and load voltage is always positive
4. none of these

ANSWER:-2

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Circuit Breaker Theory O.C.B. Advantage

Factor affecting performance of plane break oil circuit breaker:-

The factor which influence the performance of pain break oil circuit break are as follows

1. The critical length of the break
2. The speed of the contact movement. In order to extinguish the arc earlier , the speed should be high therefore double break circuit breakers are preferred.
3. The head of oil above the contacts.
4. The clearance between the live contacts and the earthed pressurized tank.

The factor which influence on increased breaking capacity are considerable head of oil and large clearances. Thus for large breaking capacity, the circuit breaker will be large.

Circuit Breaker Theory

OIL CIRCUIT BREAKER

These are one of the oldest type of circuit breaker which employs oil as ac quenching medium. The contacts of the circuit breakers are separated in the oil. The bubbles of gas formed which prevent resitriking of the arc after the current reaches zero point of the cycle. 

There are two type of circuit breakers

1. circuit breakers using large quantity of oil or the bulk oil circuit breakers

2. circuit breakers using minimum quantity of oil called minimum oil circuit breakers.

PLAIN BREAK OIL CIRCUIT BREAKER

It consists of a strong, weather tight earthed tank containing oil upto certain level and air above the oil level. both the fixed and moving contacts are immersed in oil.

 when the contacts are separated, an arc is struck between the contacts with production of large amount of heat. this with increase the temperature to near about 5000 k which will vapourize the oil into gases such as hydrogen with small percentage of methane,ethylene and acetylene. with the withdrawal of moving contacts, arc length increase and gas formation rate decreases as temperature lowers.

when distance between fixed contact and moving contact reaches at critical value, the arc gets extinguished at some current zero.

There are two types of plain- break oil circuit breakers,

1. Single break oil circuit breaker

2. double break oil circuit breaker.

Single break oil circuit breaker

The single break oil circuit breaker principle is represented in fig . The in and out of the current is through the terminal bushing. There is only one arc which is struck between the fixed and moving contact. The current breaks at one bushing and the moving contact is supported by the other bushing through sliding contact.

Double break oil circuit breaker

The principle of this type of circuit breaker is shown in the fig. There are two fixed contacts associated with terminal bushing which makes contacts with the moving contacts during normal operating condition. The lever containing the moving contacts can be operated with the help of crank.

  When the contacts are separated, two arcs are drawn. Thus there are two breaks  in series. This can achieve rapid arc lengthening which eliminates the need for a specially fast moving contact speed.

Electrical Instruments and measurements

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Q1:- The dynamometer type wattmeter is used on

       1.       ac only

       2.       dc only

       3.       ac and dc both

      4.       full wave rectified

ANSWER:-3

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Q2:- Most commonly used wattmeter is

       1.       induction type

       2.       electrostatic type

       3.       dynamometer type

       4.       moving iron type

ANSWER:-3

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Q3:- A wattmeter can be used

   

       1.       only for one rated current

       2.       for different rating current without any change

       3.       different rating current with change of connection without multimeter

      4.       with different currents with change of connections and multimeter

ANSWER:-4

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Q4:- The meter constant of energy meter is given by

       1.       rev./kw

       2.       rev./kWh

       3.       rev./watt

       4.       rev./kWhr

ANSWER:-2

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Q5:- Wattmeter are available for different rating of

     

       1.    current

       2.    voltages

       3.       currents and voltages both 

       4.       currents and voltages with change of connection without multiplier

ANSWER:-4

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Electrical Instruments and measurements

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Q1:- Moving coil permanent magnet instruments can be used on

         1.       Ac and dc

         2.       Ac only

         3.       Dc only

         4.       Half wave rectified ac

ANSWER:-3

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Q2:- The accuracy of MC instruments as compared to MI instrument is

          1.       High

          2.       Low

          3.       Same

          4.       Reasonable accuate

ANSWER:-1

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Q3:- The meter used for measuring power of the circuit is called

        

         1.       kWh meter

         2.       wattmeter

         3.       multimeter

         4.       voltmeter

ANSWER:-2

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Q4:- The cost of ammeter as compared to voltmeter is

         1.       same

         2.       higher

         3.       lower

         4.       very high

ANSWER:-3

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Q5:- A galvanometer can be used for measuring current and voltage of a circuit by

        1.       shunt only

        2.       connecting high value of resistance in series only

        3.       shunt for measuring current and high resistance in series for voltage

        4.       without in series and shunt resistance

ANSWER:-3

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Indction Motor's Questions

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Q1:- Different types of a 3- phase induction motors are

       1.       Squirrel cage

       2.       Sliping

       3.       Commutator

       4.       All of the above

ANSWER:- 4

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Q2:- The rotor of a 3-phase induction motor always runs at

      1.       Synchronous speed

      2.       Less than synchronous speed

      3.       More than synchronous speed

      4.       None of these

ANSWER:-2

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Q3:- An induction motor in general is analogous to

      1.       An auto transformer

      2.       A two winding  transformer with its secondary open circuit

      3.       A two winding transformer with its secondary winding short circuit

     4.       A three winding transformer

ANSWER:-3

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Q4:- When 3-phase supply is given to the stator of the motor a

     1.       Revolving field is set up

     2.       Pulsating field is set up

     3.       Revolving field at synchronous speed is set up

     4.       revolving field at the rotor speed is set up

ANSWER:-3

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Q5:- In a 3-phse squirrel cage induction motor, the

    
     1.       rotor conductors are kept open

     2.       rotor conductors are short circuited through end rings

     3.       ends of the rotor conductors are connected to sliping

     4.       ends of the rotor conductors are short circuited through slipped

ANSWER:-2

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Electrical Instruments and measurements

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Q1:- Tolerance of a meter is high then

1. accuracy is high
2. accuracy is low
3. accuracy is zero
4. none of the above

ANSWER:- 2

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Q2:- To decrease the tolerance of a meter 

1. accuracy should be increase
2. accuracy should be decrease 
3. accuracy should be zero
4. none of the above

ANSWER:- 1

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Q3:- Stability of a meter is opposite to 

1. readability 
2. linearty
3. sensitivity
4. tolerence

ANSWER:- 3

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Q4:- The series magnet of a single phase energy meter consists of coil of 

1. thin wire of few turns
2. thick wire of few turns
3. thick wire of more turns 
4. thin wire of more turns 

ANSWER:-2

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Q5:- The essential requirements of a single phase meter are

1. recording mechanism
2. operating mechanism 
3. moving mechanism
4. all the above

ANSWER:-3

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Electrical Measurements Qusestions

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Q1:- The scale of moving iron (M.I.) instrument is

         1.       uniform

         2.       cramped

         3.       first uniform then conjusted

         4.       none of the above

ANSWER:-2

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Q2:- Moving coil type instrument is

         1.       robust

         2.       accurate

         3.       consumes less power

         4.       possesses all the above three advantage

ANSWER:-4

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Q3:- Moving coil type instruments are

        1.       permanent magnet type

        2.       dynamometer type

        3.       induction type

        4.       permanent magnet and dynamometer type

ANSWER:-4

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Q4:- Thermal effect is used for producing deflecting torque is

        1.       wattmeter

        2.       energy meter

        3.       ammeter

        4.       all of the above

ANSWER:-3

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Q5:- Electrodynamic effect is used for the operation of

       1.       wattmeter

       2.       voltmeter

       3.       ammeter

       4.       all of the above

ANSWER:-4

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