Free Printable M3.12 Cat B

Worksheets

M3.12 Cat B

Total questions: 15

Worksheet time: 8mins

Name

Class

Date

What does a commutator do in a dc machine?

Increases the speed of the armature

Regulates the voltage in the field windings

Controls the temperature of the machine

Reverses the direction of current in the armature windings

What effect would increasing the armature current have on the armature cross field?

Reverse

No effect

Weaken

Strengthen

Which component in a dc machine machine provides the power supply for the armature?

Transformer and rotating diode pack

Commutator and brushes

Excitation winding

Field winding

Why are interpoles fitted to main poles of DC machines?

To increase armature reaction and commutation problems.

To reduce armature reaction and commutation problems.

To decrease the efficiency of the machine.

To make the machine more prone to overheating.

what is the purpose of the excitation winding in a dc machine?

To increase the machine's weight

To cool down the machine

To create the magnetic field necessary for the operation of the machine.

To reduce the efficiency of the machine

How is the direction of rotation in a dc machine changed?

By increasing the resistance in the circuit

By reducing the number of windings in the armature

By adding more voltage to the circuit

By reversing the polarity of the applied voltage or by reversing the connections to the field winding or armature.

What type of motor is best suited as a starter motor?

Shunt field motor

Series field motor

Compound motor

Stepper motor

What is the advantage of a shunt field motor?

It has a high efficiency at low speeds

It is not affected by changes in the load

It requires less maintenance

It maintains constant speed even when the load changes.

What is the advantage of a series field motor?

Low starting torque and inability to operate at variable speeds

High starting torque and inability to operate at variable speeds

Low starting torque and ability to operate at fixed speed

High starting torque and ability to operate at variable speeds

10.

What is the purpose of the commutator?

To reverse the current in the armature

To reverse the current in the field windings

To protect the slip ring from damage

To allow constant motion of the rotor

To allow the motor to be used as a generator

11.

What name is given to the current carried conductor in a motor?

Armature

Comutator

Rotor

Stator

Pole Pair

12.

What component is represented by label K

Armature Windings

Commutator

Pole Piece

Drive shaft

Yoke

13.

Which of these statements are true regarding the laminated iron core in a Rotor?

Select 1 or more answers.

It holds the armature winding in slots

It forms part of the magnetic circuit

It increases the eddy currents in the armature, therefore increases the magnetic flux

It forms part of the electric circuit

It forms the return path for the magnetic field

14.

How can Back emf be calculated

$E_b=V_s-I_aR_a$

$E_b=V_s+I_aR_a$

$E_b=\frac{V_s}{I_aR_a}$

$V_s=\frac{E_b}{I_aR_a}$

15.

With reference to Torque in a dc machine:

The magnitude of the force is proportional to

The strength of the magnetic field, Flux Density,

The current in the conductor,

The length of the conductor influenced by the magnetic field.

The value of back emf,

The current in the conductor,

The length of the conductor influenced by the magnetic field.

The value of back emf,

The current in the field windings,

The length of the conductor influenced by the magnetic field.

The value of back emf,

The current in the conductor,

The number of poles on the stator.

Reset

M3.12 Cat B

Total questions: 15

Worksheet time: 8mins

Similar Resources on Wayground