41. In the heating process of the _________ type a simple method of temperature control is possible by means of a special alloy which loses its magnetic properties at a particular high temperature and regains them when cooled to a temperature below this value.
Indirect induction over
core type induction furnace
coreless induction furnace
high frequency eddy current
Correct answer: (D) high frequency eddy current
42. One of the main advantage of the swinburn's test is
It is applicable both shunt and compound motors
It needs one running test
It is very economical and convenient
It ignores any charge in iron loss
Correct answer: (C) It is very economical and convenient
43. Out of the following methods of heating the one which is independent of supply frequency is
electric arc heating
induction heating
electric resistance heating
dielectric heating
Correct answer: (C) electric resistance heating
44. Out of the following methods of heating the one which is independent of supply frequency is
electric arc heating
induction heating
electric resistance heating
dielectric heating
Correct answer: (C) electric resistance heating
45. Regarding Ward-Leonard system of speed control which statement is false?
It is usually used where wide and very sensitive speed control is required
It is used for motors having ratings from 750kW to 4000Kw
Capital outlay involved in the system is right since it uses two extra machines
It gives a speed range of 10:1 but in one direction only
Correct answer: (D) It gives a speed range of 10:1 but in one direction only
46. Retardation test on a dc shunt motor is used for finding
Stray loss
Copper loss
Friction loss
Iron loss
Correct answer: (A) Stray loss
47. Rotating magnetic field is produced in A....
single - phase induction motor
three phase induction motor
dc series motor
ac series motor
Correct answer: (B) three phase induction motor
48. Star- delta starter of an induction motor
Inserts resistance in rotor circuit
Inserts resistance in stator circuit
Applies reduced voltage to rotor
Applies reduced voltage to stator
Correct answer: (D) Applies reduced voltage to stator
49. Synchronous capacitor is
An ordinary static capacitor bank
An over excited synchronous motor driving mechanical load
An over excited synchronous motor running without mechanical load
None of the above
Correct answer: (C) An over excited synchronous motor running without mechanical load
50. The ‘sheath’ is used in cable to
provide strength to the cable.
provide proper insulation.
prevent the moisture from entering the cable.
avoid chances of rust on strands.
Correct answer: (A) provide strength to the cable.