381. Open circuit test on transformer is used to find

- No-load current
- Full load copper loss
- Equivalent resistance referred to metering side
- Equivalent resistance referred to metering side and no-load current both

382. Transformers can be connected in

- Both series and parallel
- Series
- Parallel
- Neither series nor parallel

383. In a transformer on load the total primary current is given by

- Load component of secondary current
- Sum of magnetizing current and reflected load current on the primary side
- Reflected load current on the primary side
- Magnetizing current

384. The efficiency of a transformer depends

- On both power factor and load magnitude
- On load power factor
- On load magnitude
- Neither on load power factor nor on load magnitude

385. The no-load primary current will be approximately in the range of ________ time the rated load current in a transformer.

- 0.8
- 0.1
- 0.9
- 0.5

386. Transformers _______ Reactive power.

- Generate
- Neither generate nor absorb
- Absorb
- Absorb as well as generate

387. The short circuit test in a transformer is carried out by solidly shorting

- Only high voltage windings
- Only low voltage windings
- Either high voltage and low voltage windings
- Both high voltage and low voltage windings

388. The frequency affects

- Both hysteresis and eddy current loss
- Only eddy current loss
- Neither hysteresis nor eddy current loss
- Only hysteresis loss

389. The flux density affects

- Neither hysteresis nor eddy current loss
- Only eddy current loss
- Only core loss
- Only hysteresis loss

390. A transformer is equivalent to an ideal transformer

- With inductive coil connected in the secondary circuit
- When no coils are connected to primary and secondary
- With inductive coil connected in only the primary circuit
- With inductive coils connected in both the primary and secondary circuits

391. In a transformer the leakage flux

- Contributes to transfer of energy from primary to secondary
- Does not contribute to transfer of energy from primary to secondary
- Contributes to transfer of energy from secondary to primary
- Contributes to transfer of energy between both coils simulataneously

392. The sheet steel material used in transformer core has

- High core loss and low permeability
- Low core loss and low permeability
- Low core loss and high permeability
- High core loss and high permeability

393. Booster tranformers are used to

- To change the voltage magnitude and phase angle
- Reduce the voltage magnitude
- Increase the voltage magnitude
- To change phase angle

394. Regulation of a transformer is defined by rise in primary voltage required to maintain rated output voltage at a given power factor for a lagging power factor load

- From no load to 50% of full load
- From no load to full load
- From no load to 25% of full load
- From no load to 75% of full load

395. The short circuit test in a transformer is carried out

- At full load current
- At half load current
- At very small load current
- At greater than full load current

396. An exact equivalent circuit of a transformer is given by

- Conductance and susceptance for mutual flux
- Resistance and inductance for primary & secondary windings and conductance and susceptance to represent the mutual flux
- Resistance and inductance for primary and secondary windings respectively
- Resistance and inductance for primary , secondary and mutual flux linkages respectively

397. The no load primary input is approximately equal to the

- Iron loss of transformer
- Sum of iron loss and copper loss of transformer
- Neither iron loss of transformer nor copper loss
- Copper loss of transformer