400 Important Transformer MCQ Question and Answer | PDF Free Download
1.A single-phase transformer when supplied form 220V, 50 Hz has eddy current loss of 50W. If the transformer is connected to a voltage of 330V, 50Hz the eddy current loss will be
- A168.75W
- B112.5W
- C75W
- D50W
2.1 kVA, 230V, 50Hz single phase transformer has an eddy current loss of 30 watts. The eddy current loss when the transformer is excited by a dc source of same voltage will be
- A30 watts
- BMore than 30 W
- CLess than 30 watts
- DZero will
3.At 50 Hz operation, a single-phase transformer has hysteresis loss of 200 W and eddy current loss of 100 W. Its core loss at 60 Hz operation will be
- A432W
- B408W
- C384W
- D360W
4.On no load phasor diagram of transformer, the core loss component of the current remains in phase with
- ANo load currents
- BPrimary supply voltage
- CCore flux
- DPrimary induced voltage
5.If a sinusoidal voltage source is connected to a power transformer, it's no load current would be
- ASinusoidal and lagging the voltage by 90 degree
- BSinusoidal and lagging the voltage by less than 90 degree
- CRich in third harmonic and its fundamental would lag the voltage by 90 degree
- DRich in third harmonic and its fundamental would lag the voltage by less than 90 degree
6.The Transformer exciting current has two components, magnetizing component and core-loss component. Neglecting Impedance drop
- ABoth of them are in phase with the supply voltage
- BThe former lags the supply voltage by 90 degree while the later is in phase with supply voltage
- CBoth of the lag the supply voltage by 90 degree
- DThe former is in phase with supply voltage while the later lags the supply voltage by 90 degree
7.In a transformer, the exciting current will be in phase quadrature with the impressed voltage provided
- AOnly the leakage impedance drop is ignored
- BOnly the core loss is ignored
- CBoth the leakage impedance drop and the core loss are ignored
- DOnly the no load copper loss is ignored
8.The power factor of a power transformer on no load will be about
- AUnity
- B0.75
- C0.5
- D0.35
9.The power factor of a transformer on no load poor due to
- AMagnetizing reactance of the transformer
- BOpen circuited secondary
- CLow primary winding resistance
- DLow no load current
10.Primary winding of a transformer comprises of two identical windings in parallel. If one winding is removed, magnetizing current will be
- AHalved
- BThe same
- CDoubled
- DIncreased four times
11.The core flux of a practical transformer with a resistance load
- AIs strictly constant with load changes
- BIncreases linearly with load
- CIncreases as the square root of the load
- DDecreases with increase of load
12.The inductive reactance of a transformer depends on
- AElectromotive force
- BMagneto motive force
- CMagnetic flux
- DLeakage flux
13.The flux in transformer core
- AIncreases with load
- BDecreases with load
- CRemains constant irrespective of load
- DNone of the above
14.The mutual flux in a loaded transformer can be varied by varying
- APrimary current
- BLoad impedance
- CSecondary current
- DReluctance of the magnetic path
15.The primary ampere turns are counter balanced by
- ASecondary ampere turns
- BPrimary flux
- CIncrease in mutual flux
- DIncrease in secondary current
16.In a transformer_____ decreases with the increase in leakage flux
- APrimary induced emf
- BSecondary induced emf
- CSecondary terminal voltage
- DNone of the above
17.Power transformed from primary to secondary depends upon
- ANumber of primary turns
- BNumber of secondary turns
- CCurrent transformation ratio
- DMagnetic coupling between primary and secondary windings
18.A transformer is supplying pure resistive (unity pf) load. The
- AAbout 0.95 (lead)
- BAbout 0.95 (lag)
- CZero
- DUnity
19.In a transformer supplying inductive load
- AThe secondary current results in equivalent primary current in phase opposition
- BThe secondary terminal voltage is less than the secondary induced emf
- CThe power factor on primary side will be lower than that of load
- DAll of the above
20.The phasor diagram of transformer on load can be drawn only if we know
- AEquivalent circuit parameters of the transformer
- BLoad current
- CLoad PF
- DAll of the above