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Objective questions and answers or MCQ of Electrical Machines page-17


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266. In the adjacent figure, what kind of voltage is generated by linear movement of a horizontally or vertically loop in or counter to the direction of magnetic field?

a) A D.C. voltage
b) An A.C. voltage
c) No voltage
d) Pulse voltage

Ans: (c)

267. What kind of voltage is induced in a loop conductor rotating in an homogeneous magnetic field?

a) A.C.
b) D.C.
c) No voltage
d) Pulse voltage

Ans: (b)

268. If a loop conductor is rotated in the magnetic field, a voltage is induced in it. This voltage increases only with the

a) Density of the magnetic lines of force
b) Active length of conductor in exciting field
c) Velocity of the loop
d) Length of conductor, velocity and flux density

Ans: (d)

269. A loop conductor is rotated in a homogeneous magnetic field the magnetic flux

a) Changes its intensity constantly
b) Changes its direction with constant density
c) Changes in intensity with its direction periodically
d) Changes its intensity with its direction randomly

Ans: (c)

270. The operation of the electric generator and motor is based on the interaction between

a) Magnetic field and electric field
b) Magnetic field and electric current
c) Electric field and law of induction
d) Law of induction and dynamo-electric principle

Ans: (b)

271. What type of current is normally used to excite the synchronous and DC generators?

a) DC
b) AC single phase
c) AC three phase
d) AC two phase

Ans: (a)

272. Under what conditions will an Electromotive force be exerted on an electric conductor in a magnetic field?

a) The conductor must have diameter
b) The conductor must have current passing through it
c) Magnetic field must be intensified
d) The conductor must be in coil from

Ans: (b)

273. Which of the following statement is correct?

a) A magnetic field exerts a force on-line conductor
b) The cause of force effect lines in the fact that original magnetic field and that of line conductor affected each other
c) The repulsion takes place in the direction of mutually reducing field forces
d) All the above statements are correct

Ans: (d)

274. Which of the following transformer will have smallest size with same electrical specifications?

a) Oil Natural Air Natural (ONAN) cooled transformer
b) Dry type transformer
c) Oil Natural Air Force (ONAF) cooled transformer
d) Oil Forced Water Force (OFWF) cooled transformer

Ans: (b)

275. Which of the following Indian Standards deal with Induction motors?

a) IS: 2026
b) IS: 325
c) IS: 2208
d) IS: 3427

Ans: (b)

276. 1 H.P. is equivalent to

a) 0.746 W
b) 0.746 kW
c) 7.46 W
d) 7.46 kW

Ans: (b)

277. What kind of bushings will be used in the transformers above 33kV rating?

a) Porcelain type
b) Condenser type
c) Oil-filled type
d) (b) or (c)

Ans: (d)

278. If the percentage reactance of a power is 5.0, what will be the per unit reactance?

a) 0.05
b) 0.4
c) 1.0
d) 0.5

Ans: (a)

279. The eddy current loss in the transformer occurs in the

a) Primary winding
b) Secondary winding
c) Laminations
d) None of the above

Ans: (c)

280. A transformer with output of 250 kV at 3300 volts, has 1000 turns on its primary winding and 100 turns on secondary winding. What will be the transformation ratio the transformer?

a) 10
b) 4
c) 5
d) 3

Ans: (a)


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