ECET EEE 2012-10

1. The demagnetising flux in dc generator

A. increases emf
B. decreases emf
C. increase speed
D. decreases speed

Answer : C. increase speed
Explanation:-

2. If Ta be the torque and Is the armature current for a dc series motor, the which of the following relation is valid before saturation

A. Ta α Ia
B. Ta α (1/Ia)
C. Ta α Ia^2
D. Ta α (1/(Ia^2))

Answer : C. Ta α Ia^2
Explanation:-

3. What will happen if the back emf of a dc motor vanishes suddenly

A. The motor will stop
B. The motor will continue to run
C. The armature may burn
D. The motor will run noisy

Answer : C. The armature may burn
Explanation:-

4. The mechanical power developed by a DC motor is equal to

A. power input + losses
B. Back emf x armature current
C. Power output x losses
D. Power output x efficiency

Answer : B. Back emf x armature current
Explanation:-

5. Neglecting saturation, if current taken by a series motor is increased from 10 A to 12 A, the percentage increase in its torque is

A. 20%
B. 44%
C. 30.5%
D. 16.6%

Answer : A. 20%
Explanation:-

6. Dynamometer type instrument have

A. cramped scale at the beginning
B. cramped at the end
C. cramped at the middle
D. uniform scale

Answer : D. uniform scale
Explanation:-

7. To measure a signal of 10mv at 75Hz, which one of the following instrument can be used

A. cathode ray oscilloscope
B. VIVM
C. Moving Iron voltmeter
D. digital multimeter

Answer : A. cathode ray oscilloscope
Explanation:-

8. Which one of the following a passive transducer

A. piezoelectric
B. thermocouple
C. photovoitaic cell
D. LVDT

Answer : B. thermocouple
Explanation:-

9. The voltage coil of a single phase house energy meter

A. is highly resistive
B. is highly inductive
C. is highly capacitive
D. has a phase angle equal to load power factor angle

Answer : A. is highly resistive
Explanation:-

10. The effective value of a traingular wave is

A. Max value
B. √3(Max value)
C. √3/max value
D. max value/√3

Answer : D. max value/√3
Explanation:-