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Worksheets

Electrical Machines

Total questions: 18

Worksheet time: 14mins

Name
Class
Date
1.

____ is followed to determine the direction of coil movement for electric motors

a)

Fleming's left hand rule

b)

Faraday's left hand rule

c)

Faraday's right hand rule

d)

Fleming's right hand rule

2.

What does the thumb indicate in Fleming's left hand rule

a)

Force

b)

Current

c)

Magnetic field

d)

Voltage

3.

What is the direction of coil movement in the image shown

a)

Towards the magnet

b)

Away from the magnet

c)

In the direction of current flow

d)

Downwards

4.

Choose all that applies to a DC Shunt motor

a)

Field winding has more number of turns of thin wires

b)

High starting torque

c)

Constant Speed Motor

d)

Used in electric cars

5.

A d.c. generator whose field magnet winding is supplied from an independent external d.c. source:

a)

Self Excited DC generator

b)

Separately excited DC generator

6.

The direction of the induced emf in generators is found out using:

a)

Fleming's right hand rule

b)

Fleming's left hand rule

c)

Faraday's left hand rule

d)

Right hand thumb rule

7.

Speed of the induction motor reduces with the load applied

a)

True

b)

False

8.

The difference between the speed of the stator and the actual speed is called

(a)  

9.

____ is used to provide electrical connectivity between the static and rotating parts of the DC motor

a)

Commutator

b)

Brush

10.

Force acting on the conductor is proportional to the current in the conductor and the strength of the magnetic field

a)

True

b)

False

11.

Why does the torque and armature current characteristics of a DC shunt motor take a linear relationship?

a)

Due to constant flux

b)

Due to constant armature current

c)

Due to variations in the flux with changes in supply voltage

d)

Because the armature current is varied accordingly

12.

It is difficult to start a DC shunt motor on heavy loads:

a)

Due to large starting current requirement

b)

Due to large starting voltage requirement

c)

The residual flux present during the start of the motor is not sufficient

13.

Under normal conditions the flux and the back emf of a DC shunt motor are constant

a)

True

b)

False

14.

For a DC Shunt motor, the speed and torque characteristic is approximately similar to Torque and Armature current characteristics.

a)

True

b)

False

15.

Which motor has high starting torque

a)

DC Series Motor

b)

DC Shunt Motor

16.

Which motor develops high starting torques at low speeds and low torque at high speeds

a)

DC Series Motor

b)

DC Shunt Motor

17.

In DC Series motor the field flux becomes independent of the armature current after it reaches a saturation point

a)

True

b)

False

18.

For A DC series motor, the speed may become dangerously high if load reduces to a small value. So,

a)

It must not be run on no load

b)

It must not be run on less load at high currents