DC Motors MCQs

Question 1

Two dc series motors connected in series draw current 1 from supply and run at speed N. When the sae two motors are connected in parallel taking current I from the supply, the speed of each motor will be

Accepted Answer

4N

Answer

N

Answer

2N

Answer

N/2

Question 2

The torque-speed characteristic of a series motor is

Accepted Answer

rectangular hyperbola

Answer

parabola

Answer

linearly rising

Answer

linearly declining

Question 3

The starter for a dc motor also provides protection to the motor against damage

Accepted Answer

all of these

Answer

due to short circuit in the equipment

Answer

from long term overload

Answer

from excessive starting currents

Question 4

Starting resistor connected in

Accepted Answer

series with the armature in a dc motor

Answer

series with the field winding

Answer

parallel with the field winding

Answer

parallel with the armature

Question 5

Direct online starters are not suitable for starting large dc motors because

Accepted Answer

large voltage drop may occur in the supply mains

Answer

the starting torque becomes very low

Answer

the moto may not start

Answer

the motor may run away

Question 6

In Ward Leonard method of speed control, the minimum number of machines needed is

Accepted Answer

three

Answer

one

Answer

two

Answer

four

Question 7

Ward Leonard method of speed control is basically useful where usually

Accepted Answer

a wide range of sensitive speed control is required

Answer

a small range of very sensitive speed control is required

Answer

a wide range of less sensitive speed control is required

Answer

a narrow range of less sensitive speed control is required

Question 8

In Ward Leonard method of speed control, the lower limit of speed is caused bY

Accepted Answer

residual magnetism of the generation

Answer

core losses of motor

Answer

mechanical losses of motor and generator together

Answer

all of the above

Question 9

In a permanent magnet de motor which of the following methods of speed control can not be used?

Accepted Answer

field current variation

Answer

armature voltage variation

Answer

armature resistance control

Answer

all of these