# Transformer MCQ

### 1.The basic function of a transformer is to change

• AThe level of the voltage
• BThe power levels
• CThe power factor
• DThe frequency

The level of the voltage

Explanation:

### 2.In an ordinary transformer which of the following does not change

• AVoltage
• BCurrent
• CFrequency
• DAll of the above

Frequency

Explanation:

• A50%
• B60%
• C80%
• D95%

95%

Explanation:

### 4.In a transformer, electrical power is transferred from primary to secondary

• AThrough air
• BBy magnetic flux
• CThrough insulating medium
• DNone of these

By magnetic flux

Explanation:

Explanation:

### 6.Transformer action requires a

• AConstant magnetic flux
• BIncreasing magnetic flux
• CAlternating magnetic flux
• DAlternating electric flux

Alternating magnetic flux

Explanation:

### 7.The flux created by the current flowing through the primary winding induces emf in

• APrimary winding only
• BSecondary winding only
• CTransformer core only
• DBoth primary and secondary windings

Both primary and secondary windings

Explanation:

### 8.The primary and secondary windings of a power transformer always have

• AA common magnetic flux
• BSeparate magnetic circuits
• CWire of same size
• DSame number of turns

A common magnetic flux

Explanation:

### 9.The iron core in a transformer provides a _____path to the main flux

• ALow reluctance
• BHigh reluctance
• CLow resistance
• DHigh conductivity

Low reluctance

Explanation:

### 10.If rated dc voltage is applied instead of ac to the primary of a transformer

• ASecondary of transformer will burn
• BPrimary of transformer will burn
• CSecondary voltage will be excessively high
• DThere will be no secondary voltage

Primary of transformer will burn

Explanation:

### 11.A transformer transforms

• AVoltage
• BCurrent
• CVoltage and current
• DFrequency

Voltage and current

Explanation:

### 12.For an ideal transformer the windings should have

• AMaximum resistance on primary side and least resistance on secondary side
• BLeast resistance on primary side and maximum resistance on secondary side
• CEqual resistance on primary and secondary sides
• DNo ohmic resistance on either side.

No ohmic resistance on either side.

Explanation:

### 13.The core flux in transformer depends mainly on

• ASupply voltage
• BSupply voltage and frequency
• CSupply voltage frequency and load
• DSupply voltage and load but independent of frequency

Supply voltage and frequency

Explanation:

• A1
• B100
• C0.01
• D0.1

100

Explanation:

### 15.If the applied voltage to a transformer primary is increased by keeping the V/f ratio fixed, then the magnetizing current and the core loss will, respectively:

• ADecrease and remain the same
• BIncrease and decrease
• CBoth remain the same
• DRemain the same and increase

Remain the same and increase

Explanation:

### 16.If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced to 50% (assuming that the magnetic circuit remain unsaturated), the maximum core flux density will

• AChange to three times the original value
• BChange to 1.5 times the original value
• CChange to 0.5 times the original value
• DRemain the same as the original value

Change to three times the original value

Explanation:

### 17.The applied voltage of a certain transformer is increased by 75%; while the frequency of the applied voltage is reduced by 25%. The maximum core flux density will

• AIncrease by seven times
• BIncrease by three times
• CReduce to one quarter
• DRemain the same

Increase by three times

Explanation:

### 18.If the supply frequency of a transformer is increased, keeping the supply voltage constant, then

• ABoth magnetizing component and core loss component of current ill decrease
• BBoth magnetizing component and core loss component of current will increase
• CMagnetizing component of current will increase while core loss component of current will decrease
• DMagnetizing component of current will decrease while core loss component of current will increase

Both magnetizing component and core loss component of current ill decrease

Explanation:

• A230V
• B460V
• C115V
• D65V

115V

Explanation:

### 20.A single-phase transformer rated for 220/240V, 50Hz operates at no load at 220 V, 40 Hz. This frequency operation at rated voltage results in which one of the following?

• AIncrease of both eddy-current and hysteresis losses.
• BReduction of both eddy-current and hysteresis losses
• CReduction of hysteresis loss and increase in eddy-current loss.
• DIncrease of hysteresis loss and no change in the eddy-current loss