Chapter 7, Problem 36R

To determine

To Label: The parts of the device in the diagram and explain the function of each.

Explanation of Solution

A simple electric motor is shown in the question.

The function of each part of the motor is as follows:

1. Permanent magnet
Function:the permanent magnet provides the magnetic field due to which the magnetic force between the coil and the magnet makes the coil rotate, if there is current in the coil.
2. Brushes
Function: the brushes in an electric motor work as conducting pad connected to the battery. When the brushes make contact with the commutator, there exists current in the coil due to which the col rotates.
3. Commutator
Function: the commutator is a split conducting metal ring. Along with the brushes, it forms a closed circuit between the battery and the coil. When it is in contact with the brushes, current flows through the coil.

The commutator also reverses the direction of current in the coil by rotating in such a way that its halves connected to the positive and negative terminal of the battery are switched. This results in flipping of the polarity of the magnetic field around the coil.

4. Battery
Function: the battery produces the required voltage difference across the device due to which current flows in the coil.
5. Coil
Function: the coil acts as an electromagnet when current flows through it. The continuous rotation of the coil, aided by the battery, shows the conversion of electric energy into mechanical energy.

Conclusion: The electric motor transforms electric energy into mechanical energy due to the operation of each part.