ECET EEE 2010-1

1. The function of Commutator in a DC Machine is

A) to improve commutation
B) to change ac current to dc current
C) to change ac voltage to dc current
D) to provide easy speed control

Answer : to change ac current to dc current
Explanation:-

2. If the number of poles in a lap wound dc generator increased by a factor of 2, the generated emf will

A) increased by a factor of 2
B) decreased by a factor of 2
C) increased by a factor of 4
D) Remain the same

Answer : Remain the same
Explanation:-

3. Speed of dc shunt motor can be increased by

A) Increasing the resistance in the field circuit
B) Increasing the resistance in the armature circuit
C) Decreasing the resistance in the field circuit
D) Decreasing the resistance in the armature circuit

Answer : Increasing the resistance in the field circuit
Explanation:-

4. A starter is used in a dc motor because

A) It is not self starting
B) Initially back emf is zero and armature current is high
C) It is necessary to overcome back emf
D) Its resistance is very high

Answer : Initially back emf is zero and armature current is high
Explanation:-

5. If the field winding of a running shunt motor suddenly breaks open

A) Its speed slows down
B) It stops at once
C) It gives out sparks
D) Its speed becomes dangerously high

Answer : Its speed becomes dangerously high
Explanation:-

6. The direction of rotation of a dc motor may be reversed by

A) Reversing the supply voltage
B) Adding resistance to the field circuit
C) Reversing armature connection
D) Interchanging the armature and field connection

Answer : Reversing armature connection
Explanation:-

7. When an electric train moves down hill, the dc motor acts as

A) dc series generator
B) dc shunt generator
C) dc shunt motor
D) dc compound motor

Answer : dc series generator
Explanation:-

8. Moving coil instrument can be used for measuring at

A) High frequencies
B) Low frequencies
C) Only dc
D) both dc and ac

Answer : Only dc
Explanation:-

9. Sensitivity of a voltmeter is expressed as

A) Volts/ohm
B) Ohms/volt
C) Ohms volt
D) Siemen/volt

Answer : Ohms/volt
Explanation:-

10. Transducer is a device which

A) converts one form of power into an other
B) Converts one form of energy into an other
C) Helps in measuring electrical signal
D) Is similar to a transformer

Answer : Converts one form of energy into an other
Explanation:-