Transformer questions

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Q1:- what is meant by the leakage flux of transformer
1. It is the flux which is linked with the primary and the secondary winding
2. It is that part of the magnetic flux which is significant for radio interference
3. It is the magnetic flux which is linked the only with the primary or only with the secondary winding
4. The leakage flux in the transformer is the influx whose path is exclusively through the air

ANSWER:-3

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Q2:- why are Transformer core laminated

1. Laminated core are cheaper than solid Core

2. There are fewer Eddy current losses in laminated Core

3. There are fewer hysteresis losses in laminated Core

4. There is less coming as compared to solid Core

ANSWER:-2

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Q3:- hysteresis loss in a transformer depends upon the

1. Applied voltage
2. Type of core material
3. Number of laminations
4. Reactance of the winding

ANSWER:-2

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Q4:- current transformer is used to measure 100 A current by 5 ampere metre the current transformer is a

1. Step Up transformer
2. Step down transformer
3. Power transformer
4. Distribution transformer

ANSWER:-1

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Q5:- it is economical to use an auto transformer when the Transformer ratio is

1. Low
2.high
3. Neither too high no to low
4. None of these

ANSWER:-1

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Electrical questions

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Q1:- when is the mechanical power developed by a DC motor maximum
1. Back EMF is equal to applied voltage
2. Back EMF is equal to zero
3. Back EMF is equal to the half of applied voltage
4. None of the above

ANSWER:-3

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Q2:- internal characteristic of a DC generator is plotted between the

1. Field current and voltage generated no load

2. Armature current and voltage generated no load

3. Armature current and voltage generated after armature reaction

4. Field current and voltage generated on load

ANSWER:-3

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Q3:- the bridge method in transformer will

1. Check Transformer winding
2. Check windings voltages
3. Find ratio of induced voltage
4. Result in short circuit loss

ANSWER:-3

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Q4:- what is the effect of the field failure of salient pole synchronous motor connected with infinite bus

1. Reduce motor torque and speed
2. Not charged motor torque and speed
3. Stop the motor
4. Reduce not at work but motor will continue to run at synchronous speed

ANSWER:-4

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Q5:- Wanger's earthing device is used in AC Bridge for

1. Shielding the bridge element
2. Eliminating the dtray electrostatic field effect
3. Eliminating the effect of earth capacitance
4. Eliminating the effect of the inter component capacitance

ANSWER:-2

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Competitive exams questions

Q1:- in which of the following Transformers is the secondary winding always kept closed
1. Current transformer
2. Potential transformer
3. Power Transformers
4. Distribution transformer

ANSWER:-1

Q2:- two holes are drilled in the disc on a diameter of energy metre to

1. Increase ventilation

2. Reduce the weight of disc

3. Eliminate creeping on no load

4.Increase deflecting torque

ANSWER:-3

Q3:- which of the following instruments has the highest torque/ weight ratio among the given instrument

1. Attraction type MI instrument
2. Repulsion type MI instrument
3. Permanent magnet moving coil instrument
4. Electrodynamometer instrument

ANSWER:-3

Q4:- if current through the operating coil of moving iron instrument is doubled the operating force becomes

1. One and a half Times
2. 2times
3. 3 times
4. 4 times

ANSWER:-4

Q5:- in moving iron instruments the iron moves in a direction to cause

1. Coil inductance to be constant
2. Mutual inductance to be minimum
3. Minimum reluctance path
4. Decrease in the flux passing through it

ANSWER:-3

DC machine

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Q1:- the direction of rotation of a DC motor is reversed by
1. Riveting armature connections
2. Interchanging the armature and field connections
3. Adding resistance to the field circuit
4. Reversing supply connections

ANSWER:-1

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Q2:- the s i unit of conductivity is

1. Ohm metre

2. Ohm per metre

3. Mho meter

4.mho/m

ANSWER:-4

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Q3:- a piece of oil soaked paper has been inserted between the plates of a parallel plate capacitor then the potential difference between the two plates will be

1. Increase
2. Decrease
3. Remains unchanged
4. Become zero

ANSWER:-2

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Q4:- the current drawn by tungsten filament lamp is measured by an ammeter. the ammeter reading under steady state condition will be the ammeter reading when the supply is switched on

1. Same as
2. Less than
3. Greater than
4. Double

ANSWER:-2

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Q5:- Tesla is same as

1. Weber per metre
2. Weber metre square
3. Farad /metre
4. Henry per metre square

ANSWER:-2

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DC machine

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Q1:-which of the following statement is correct in case of single phase transformer ?

1.in this a varying current appears in primary winding that creates varying magnetic flux in transformer's core
2.it creates varying magnetic field in secondary winding that induces electromotive force (EMF) or voltage 
3.it carries inductive coupled conductor
4.all of the above 

ANSWER:-4

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Q2:-the surge impedance of over head transmission lines range from

1.30 to 60 ohms

2.300 to 600 ohms

3.2500 to  6500 ohms

4.10000 to 40000ohms

ANSWER:-2

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Q3:-Nodal analysis applies to 

1.KVL & ohm's law
2.KCL  & superposition
3.KVL & superposition 
4.KCL & superposition

ANSWER:-2

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Q4:- in a DC machine how are the computing pole winding connected

1. In series with shunt winding
2. Parallel to the shunt winding
3. In series with the armature winding
4. Parallel to the armature winding

ANSWER:-3

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Q5:- which of the following winding is connected in series with armature winding of DC machine

1. Series winding
2. Auxiliary series winding
3. Compensating winding
4. Communicating on winding

ANSWER:-4

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DC Machine

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Q1:-The efficiency of a motor is generally expressed as 

1. 90 %
2. 75 %
3. 60 %
4. 99 %

ANSWER:-1

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Q2:-The efficiency of a generator is usually expressed as 

1. (input - losses ) / input
2. output / input 
3. output /(output+input)
4.  none of these 

ANSWER:-3

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Q3:-In swinburne test on a dc machine 

1. all the losses cannot be determined individually
2. copper losses  cannot be determined individually
3. mechanically and iron losses can not be determined individually
4. none of the above

ANSWER:-2

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Q4:-Two  dc machines 500 kw each are tested by Hopkinson test. The power input would be of the order of 

1. 500 kw 
2. 100 kw
3. 1000 kw
4. none of these

ANSWER:-2

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Q5:-The no load voltage of a generator is 230 v and the rated load voltage is 200 v then the voltage regulation

1. 5%
2. 10%
3. 15%
4. 20%

ANSWER:-3

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DC Machine

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Q1:-A shunt generator has a speed of 500 rpm when delivering 100 kw at 200 v. it run as a motor taking an input of 100 kw from 200 v mains the speed will be 

1. 500 rpm
2. less than 500 rpm
3. more than 500 rpm
4. none of these 

ANSWER:-2

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Q2:-Swinburne test can not be used or 

1. series motor
2. shunt motor
3. compound motor
4. none of these

ANSWER:-1

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Q3:-In Hopkinson test on a pair of shunt machines 

1. the armature currents of the motor and generator are equal
2. the armature current of the motor is less than that of generator
3. the armature current of the generator is less than that of the motor 
4. none of these 

ANSWER:-2

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Q4:- In a dc machine the maximum losses occur due to 

1. iron losses
2. mechanical losses
3. copper losses
4. none of these

ANSWER:-3

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Q5:-The efficiency of a motor is generally expressed as

1. (input -losses) / input
2. output / input
3. output / (output+losses)
4. none of the above

ANSWER:-1

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