Magnetism and Current Flow Direction

After reading this section you will be able to do the following:

  • Discuss what happens to the electromagnet when the current is reversed.


  1. What happens each time you reverse the electrical current in the wire?
  2. What would happen if we used alternating current (AC) instead of direct current (DC) in the wire?

In the previous experiment, you saw how magnetism makes it possible to convert mechanical energy into electrical energy, allowing electric generators to make electricity. In this experiment and the next experiment, we see that magnetism can also let us do the opposite; that is, we can convert electricity into mechanical energy. In the experiment you just finished, when you turn the current on, the current flows through the wire and temporarily magnetizes the bar of iron material. One end of the magnet becomes a north pole and the other end becomes the south pole.

When you reverse the direction of the current flowing in the wire, the north and south poles are also reversed. When you reverse the current again, the north and south poles reverse again. In fact, each time the current is reversed, the north and south poles will exchange places. Direct current (DC) flows in only one direction through a wire. So, in order to change the direction of flow change, there needs to be a reversing switch. As you will see in the next experiment, alternating current (AC), on the other hand, is constantly changing its direction of flow, so a reversing switch is not necessary.