D.C. Motor

A simple d.c. electric motor is shown in the diagram.

Which of the following changes would make the coil turn more quickly?

• Reducing the strength of the magnetic field

• Reversing the direction of the current and swapping the magnetic poles

• Swapping the magnetic poles

• Increasing the current in the coil

A class is designing a d.c. motor. To achieve a greater turning effect, three suggestions are made.

1. Have larger current in the coil of the motor

2. 2. Have a stronger magnet in the motor

3. 3. Put a larger number of turns on the coil

4. Which suggestions will help to increase the turning effect?

• 1, 2 and 3

• 1 and 2 only

• 1 and 3 only

• 2 and 3 only

A student makes a small d.c. motor. The teacher supplies the following equipment

1. 1. battery

2. 2. ammeter

3. 3. voltmeter

4. 4. coil of wire

5. 5. magnets

6. 6. resistor

7. The student is also able to use other equipment if he wishes.

8. Which equipment must be used?

• ammeter, battery and resistor

• ammeter, coil of wire and voltmeter

• battery, coil of wire and magnets

• magnets, resistor and voltmeter

What is the role of the split ring commutator in a d.c. motor?

• The split ring commutator increases the speed of the motor.

• The split ring commutator regulates the voltage in the motor.

• The split ring commutator reverses the direction of current in the armature coil.

• The split ring commutator reduces the friction in the motor.

How can you determine the direction of turning of the coil in a d.c. motor using Fleming's left hand rule?

• The direction of turning of the coil can be determined by the direction in which the thumb points.

• The direction of turning of the coil can be determined by the direction in which the pinky finger points.

• The direction of turning of the coil can be determined by the direction in which the index finger points.

• The direction of turning of the coil can be determined by the direction in which the middle finger points.

What happens if the direction of the current in the armature coil is reversed in a d.c. motor?

• The motor will rotate in the opposite direction for a short period and then stop.

• The direction of the motor's rotation will be reversed.

• The motor will rotate faster.

• The motor will stop working.

The diagram shows a simple d.c. motor. Which part needs to be made of soft iron to increase the efficiency of the motor?

• A

• B

• C

• D

The diagram shows a simple DC electric motor which is rotating.

Which change will make the motor rotate more quickly?

• reversing the polarity of the magnets

• reversing the battery

• removing the magnets

• using more powerful magnets

A coil carries a current in a magnetic field. The coil experiences a turning effect.

Which device uses this effect?

• a DC motor

• an electromagnet

• a relay

• a transformer