# ONLINE Multiple Choice Questions – Electric Machine Design PART 15

211. In case of transformers, with increasing frequency
(A) copper losses reduce but efficiency increases
(B) copper losses increase but efficiency decreases
(C) both copper losses and efficiency increase
(D) copper losses remain unaffected while efficiency increases.

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212. The regulation of a transformer is least affected by changes in frequency at
(A) leading power factor
(B) lagging power factor
(C) unity power factor
(D) all of the above.

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213. In case of induction motor, with increase in supply voltage, which of the following increases ?
(A) Power factor
(B) Slip
(C) Torque
(D) All of the above.

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214. In most AC machines, it is usually a standard practice to use
(A) fractional slot winding With full-pitch coils
(B) fractional slot winding with chorded coils
(C) integral slot winding with chorded coils
(D) integral slot winding with full pitch coils.

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215. In a transformer iron losses vary as __________ of
voltage
(A) inverse
(B) inverse square
(C) square
(D) cube.

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216. In case of distribution transformers, at fractional loads
(A) with increase in voltage efficiency decreases
(B) with increase in voltage efficiency increases
(C) with decrease in voltage efficiency decreases

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217. In case of transformers regulation varies as
(A) inverse of voltage
(B) square of voltage
(C) inverse square of voltage
(D) voltage.

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218. In a transformer, with change in frequency
(A) copper losses increase
(B) copper losses decrease
(C) copper losses remain unchanged.

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219. Distribution transformer has core losses
(A) > copper losses
(B) = copper losses
(C) ∞ copper losses
(D) = 1/2 copper losses.

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220. If a synchronous motor fails to start, the probable cause could be
(A) low voltage
(B) too much load at starting
(C) single phasing
(D) any of the above.

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221. In case a synchronous motor starts but fails to develop full torque, the probable cause could be
(A) low excited voltage
(B) reverse field winding
(C) open or short circuit
(D) any of the above.

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222. If a DC machine gives shock the probable cause could be
(A) armature field coils or brush holders earthed
(B) weak or leaky insulation
(C) loose earth wire
(D) all of the above.

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223. If a DC motor stops after running for some time, the probable cause could be any of the following EXCEPT:
(A) Weak or no field
(B) Brushes ahead of neutral
(C) Insufficient power supply
(D) Insufficient torque developed.

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224. If fuse blows at the starting of a DC motor the probable cause could be
(A) low capacity of the fuse
(B) overload
(C) short circuit in the starter resistance
(D) any of the above.

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225. Sound in a DC motor may be due to
(A) unequal resistance of the armature and field coils
(B) loose fittings of the field core with yoke or frame
(C) improper fitting of the side covers
(D) any of the above.

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