- An electric motor converts electrical energy to kinetic energy.
- The diagram above shows the structure of a simple direct current motor (DC motor).
- It consists of a rectangular coil of wire placed between 2 permanent magnets.
- The coil is soldered to a copper split ring known as a commutator. 2 carbon brushes are held against the commutator.
- The function of the brush is to conduct electricity from the external circuit to the coil and allow the commutator to rotate continuously.
- The function of the commutator is to change the direction of the current in the coil and hence change the direction of the couple (the 2 forces in opposite direction) in every half revolution. This is to make sure that the coil can rotate continuously.
- The operation principle of a direct current motor is explained in detail in the second Youtube video below.
SPM Physics – Direct Current Motor
In this video, our tutor explains the important point that SPM students need to know to prepare for their exam.
This video shows how the commutator changes the direction of the current in the coil, and hence change the direction of the force in every half revolution. Pay attention to the change of direction of the force in every half revolution.
This is a very long video, discussing how the force is produced by the interaction between a current-carrying conductor in a magnetic field and its application in the direct current motor.