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SSC JE 2019-20 Technical Quiz 37

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Question 1

The supply voltage to an induction motor is reduced by 10%. By what percentage, approximately, will the maximum torque decrease?

Question 2

A 3-phase, 400 V wound rotor motor has delta-connected stator winding and star connected rotor winding. The stator has 48 turns/phase while the rotor has 24 turns/phase. The standstill voltage across the slip rings is

Question 3

A 3-phase induction motor is connected to a supply of normal voltage. The e.m.f. induced between the slip rings at standstill is

and the resistance and standstill reactance/phase are

and

respectively. The rotor is joined to a star-connected resistance of

/phase. The rotor phase current at starting will be

Question 4

To save wastage which lamp is the cheapest?

Question 5

The quantity of heat absorbed from the heater by convection depends upon

Question 6

Due to which one of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

Question 7

An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be

Question 8

The short-circuit ratio of a typical synchronous machine is obtained from the OCC and SCC curves of Fig.2 as