1. The speed of a series motor at no load is ?

infinity

4000 r.p.rn.

2000 r.p.m.

1000 r.p.m.

Answer: infinity

Explanation:


2. In D.C. machines the residual magnetism is of the order of ?

2 to 3 per cent

10 to 15 per cent

20 to 25 per cent

50 to 75 per cent

Answer: 2 to 3 per cent

Explanation:


3. Which of the following statements is correct, in case of a D.C. series motor ?

It should be directly connected to the load

It may run away if its field becomes open

It is a constant speed motor

It cannot be used where high starting torque is required

Answer: It should be directly connected to the load

Explanation:


4. Which D.C. motor will have least percentage increase of input current, for the same percentage increase in the torque ?

Shunt motor

Series motor

Cumulative compound motor

Separately excited motor

Answer: Series motor

Explanation:


5. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens ?

nothing will happen to the motor

this will make armature to take heavy current, possibly burning it

this will result in excessive speed, possibly" destroying armature due to excessive centrifugal stresses

motor will run at very "slow speed

Answer: this will result in excessive speed, possibly" destroying armature due to excessive centrifugal stresses

Explanation:


6. Which loss in a D.C. generator varies with load ?

Copper loss

Eddy current loss

Hysteresis loss

Windage loss

Answer: Copper loss

Explanation:


7. In which of the following tests only one motor is required ?

Brake test

Hopkinson's test

Field's test

Swinburne's test

Answer: Brake test

Explanation:


8. Three point starter can be used for ?

series motor only

shunt motor only

compound motor only

both shunt and compound motor

Answer: both shunt and compound motor

Explanation:


9. In DC. motor which of the following can sustain the maximum temperature rise ?

Slip rings

Commutator

Field winding

Armature winding

Answer: Field winding

Explanation:


10. Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of ?

D.C. series motor

D.C. shunt motor

induction motor

all of above motors

Answer: D.C. series motor

Explanation: