Page 156 - Physics Form 5 KSSM_Neat

Activity 4.6 shows that the speed of rotation of an electric motor increases when:

Current in the Strength of magnetic Coil with more turns
coil increases field increases is used

KEMENTERIAN PENDIDIKAN MALAYSIA

Activity 4.7 CPS ICS

Aim: To study the direct current motors found in used devices to identify the arrangement of the
coil and the commutator
Instructions:
1. Collect a few direct current electric motors from used devices.
2. With the aid and guidance of your teacher, dismantle each motor and identify the coil, the
magnet and the commutator.
3. Observe the position of the coil and the magnet in the motor.
4. Observe also the number of sections in the commutator.
5. Prepare a brief report that compares and contrasts the arrangement of the coil, magnet and
commutator in direct current motors.

While carrying out Activity 4.7, you may have come across electric motors which do not have
a commutator and carbon brushes. Photograph 4.3 shows a brushless motor and a brushed motor.
What is the advantage of brushless motors?

Brushless Motor Brushed Motor

Carbon brush

Magnet
Commutator
Coil
Magnet

Axle Coil

Photograph 4.3 Brushless motor and brushed motor
146 LS 4.1.6