ECET EEE 2011-8

1. In a DC series motor, the field flux is

A. nearly constant
B. proportional to armature current
C. inversly proportional to field current
D. proportional to square of the armature current

Answer : D. proportional to square of the armature current
Explanation:-

2. In a DC shunt motor, at 20A of load current the torque developed is 30 Nm. If the load current is doubled, the torque changes to

A. 60 Nm
B. 45 Nm
C. 30 Nm
D. 120 Nm

Answer : C. 30 Nm
Explanation:-

3. Hysteresis and Eddy current losses in electrical machines depend on

A. flux density
B. speed
C. speed and flux density
D. voltage

Answer : A. flux density
Explanation:-

4. The efficient way of obtaining damping torque in electrical instruments is

A. air-friction damping
B. fluid friction damping
C. hysteresis damping
D. eddy current damping

Answer : D. eddy current damping
Explanation:-

5. Induction type wattmeters mainly operates on which effect?

A. eddy currents flow
B. thermo-static effect
C. thermo-electric effect
D. photo-voltaic effect

Answer : A. eddy currents flow
Explanation:-

6. Basically, a megger is a

A. moving-iron type of instrument
B. electro-static type of instrument
C. hot-wire type of instrument
D. moving coil type of instrument

Answer : B. electro-static type of instrument
Explanation:-

7. The thermocouple instrument will measure

A. temperature
B. voltage
C. speed
D. flux

Answer : A. temperature
Explanation:-

8. The load sharing between two transformers operating in parallel, is according to their

A. efficiency
B. pu impedance
C. rating
D. leakage reactance

Answer : C. rating
Explanation:-

9. The primary and secondary induced emf's E1 and E2 in a two winding transformer are always

A. equal in magnitude
B. in-phase with each other
C. anti-phase with each other
D. depends on the type of the transformer

Answer : C. anti-phase with each other
Explanation:-

10. A 200KVA transformer has an iron loss of 1KW and full load copper loss of 2KW. The load KVA, corresponding to maximum efficiency is

A. 50 kva
B. 100 kva
C. 141.1 kva
D. 200 kva

Answer : C. 141.1 kva
Explanation:-
The load KVA corresponding to maximum efficiency = KVA*Sqrt(Pi/Pcu)
= 200*sqrt(1/2)
= 141.1 KVA