501 MCQ Questions on Transformer

316. As compared to an amplifier, a transformer cannot

(a) decrease the output voltage.
(b) increase the input current.
(c) increase the output power.
(d) none of these. [MP JE 2016]

317. What is the energy efficient transformer core made up of? [MP JE 2016]

(a) Silicon alloyed iron (grain oriented)
(b) Iron
(c) Amorphous core-metallic glass alloy
(d) None of these

318. Two transformers when operating in parallel will share the load depending upon their

(a) alternating current.
(b) inductive reactance.
(c) per unit impedance.
(d) efficiency. [MP JE 2016]

319. If a transformer has hysteresis loss of 10 watts on AC and is changed to DC supply of the same magnitude, then the hysteresis loss will be

(a) double.
(b) half.
(c) zero.
(d) none of these. [MP JE – 2016]

320. A transformer having 1000 primary turns is connected to a 250 V ac supply. For a secondary voltage of 400 V, then number of secondary turns should be

(a) 1600
(b) 250
(c) 400
 (d) 1250 [MP JE 2016]

321. Ferrite cores are used in high frequency transformer, because it has

(a) average permeability.
(b) low hysteresis.
(c) low impedance.
(d) high resistance. [MP JE 2016]

322. The efficiency of ………. is more than 90%.

(a) motor
(b) transformer
(c) generator
(d) none of these

323. Which part of the transformer is constructed by the L, I and E type of laminated steel?

(a) Coils
(b) Insulating Materials
(c) Magnetic core
(d) Tank and Cooling system

324. Which type of connection is used for both large voltage and low voltage rating transformers? [MP JE – 2016]

(a) Delta-Delta connection
(b) Delta-Wye connection
(c) Wye-Wye connection
(d) Wye-Delta connection

325. Which type of transformer is used to conduct assessment at high and ultra-high voltages? [MP JE – 2016]

(a) Power transformer
(b) Testing transformer
(c) Radio transformer
(d) Auto transformer

326. In which type of immersed transformer, the oil is pumped through windings to extract heat from oil? [MP JE – 2016]

(a) Oil immersed water cooled transformer.
(b) Oil immersed forced air cooled transformer.
(c) Oil immersed forced oil cooled transformer.
(d) Oil immersed self cooled transformer.

327. The reason why open circuit test is performed on the low voltage of the winding is that it

(a) needs minimum power input.
(b) draws large current to facilitate reading.
(c) requires less voltage to perform the test.
(d) involves less core losses. [LMRC – 2015]

328. The value of flux involved in the emf equation of transformer is

(a) instantaneous
(b) maximum
(c) average
(d) rms [RRB JE – 2015]

329. The essential condition for parallel operation of two single phase transformers is that they should have the same

(a) polarity
(b) kVA rating
(c) voltage ratio
(d) percentage impedance

330. Assertion A: A distribution transformer has low flux density.

Reason B: It is constantly connected to the supply.

Which of the following is correct? [UPPCL – 2016]
(a) A and B are true, but B is not the correct explanation of A.
(b) A and B are true, and B is the correct explanation of A.
(c) A is true, but B is false.
(d) B is true, but A is false.

331. In a transformer, the applied voltage leads the no-load current by an angle of

(a) 75°
(b) 90°
(c) 180°
 (d) 45° [UPPCL – 2016]

332. The number of secondary turns of a coil in a transformer is 4 times the number of turns in primary coil. If the voltage in primary coil is 200 V, the secondary voltage would be

(a) 800 V
(b) 50 V
(c) 200 V
(d) 2000 V [UPPCL – 2016]

333. Which of the following is/are the requirements of a good transformer oil? [UPPCL – 2016]

1. Low Viscosity
2. Low Volatility
3. High Viscosity
4. High Volatility

(a) Only 1 and 2
(b) Only 3 and 4
(c) Only 1 and 4
(d) Only 2 and 3

334. The magnitude of mutual flux in a transformer

(a) is same at all loads.
(b) is constant at high loads but varies at low loads.
(c) varies at high loads.
(d) varies at low loads. [UPPCL – 2016]

335. Which test helps in determining the efficiency of two identical transformers under load conditions? [UPPCL – 2016]

(a) Back to Back Test
(b) Short Circuit Test
(c) No such test exists
(d) Open Circuit Test

336. The Potential transformer’s Nominal Ratio is defined as the ratio of

(a) primary winding voltage and secondary winding voltage.
(b) rated primary winding voltage and rated secondary winding voltage.
(c) primary windings turns and secondary winding turns.
(d) any of these. [DMRC – 2016]

337. In which type of windings extra insulation between layers is required in addition to insulation of conductors?

(a) Cross over windings
(b) Continuous disc windings
(c) Sandwich windings
(d) Helical windings

338. In current transformer

(a) secondary winding must be closed.
(b) secondary winding must be open.
(c) primary winding must be closed.
(d) primary winding must be open. [UPSSC JE 2016]

339. A transformer may have two or more ratings depending upon the type of

(a) insulation used.
(b) winding.
(c) core used.
(d) cooling used.

340. The 25 kVA transformer has a voltage ratio 3300/400V. Find the primary current.

(a) 6.25 A
(b) 75.8 A
(c) 62.5 A
(d) 7.58 A

341. The core in a large power transformer is unit of

(a) mild steel.
(b) ferrite.
(c) cast iron.
(d) silicon steel.

342. Power transformed from primary to secondary in a transformer depends upon:

(a) number of primary turns.
(b) transformation ratio.
(c) number of secondary turns.
(d) magnetic coupling between windings. [LMRC – 2015]

343. In a transformer, variable losses = 600 W, hysteresis loss 20 W and Iron loss = 500 W. What is magnitude of Eddy current losses? [UPPCL  (AE) – 2016]

(a) 1120 W
(b) 100 W
(c) 480 W
 (d) 1080 W

344. Consider the following given statements about auto-transformers and choose the one which is/ are correct. [UPRVUNL AE – 2014]

1. Auto-transformers require less copper is compared to a conventional, 2-winding transformer of the same capacity.
2. Auto-transformers provide isolation between the primary and secondary windings.
3. Auto-transformer has less leakage reactance as compared to the conventional, 2-winding transformer of the same capacity.

(a) Only 1 and 2
(b) Only 1 and 3
(c) Only 2 and 3
(d) Only 1

345. If frequency of a transformer is increased 3 times, maximum flux density in the core

(a) increases 3 times.
(b) decreases 3 times.
(c) increases 9 times.
(d) decreases 9 times. [UPPCL AE – 2016]

346. Voltage regulation in a transformer is always positive at all…..

(a) lagging p.f. load.
(b) zero p.f.
(c) lagging and unity p.f. loads.
(d) leading p.f. loads. [UPPCL AE 2016]

347. Short circuit test is conducted at…. side while……. side is…….

(a) H.V., L.V., short circuited with thick conductor
(b) L.V., H.V., short circuited with thick conductor
(c) H.V., L.V., open circuited
(d) L.V., H.V., open circuited with thin conductor

348. Primary current in a current transformer is increased to a very high voltage. It will cause

(a) increase in ratio error.
(b) increase in phase angle error but decrease in ratio error.
(c) reduction in both ratio error and phase angle.
(d) increase in phase angle error only.

349. T-T scott connection is suitable for

(a) large HV transformers.
(b) small HV transformers.
(c) supply networks.
(d) AC motor starting. [UPPCL AE – 2016]

350. A shell type transformer has ……… limbs and ……. yoke. [UPPCL AE 2016]

(a) 2, 1
(b) 2, 2
(c) 3, 2
(d) 2, 3