Magnetism

You know that charged objects can attract or repel other objects. You may have had a chance to investigate magnets. You might have a pair of bar magnets that you use to investigate magnet properties. If you have then you are probably aware that magnets can both repel and attract just like electrically charged objects. Magnets have polarity. We refer to these as north and south poles. With magnets, like poles repel, unlike poles attract and both north and south poles attract materials that aren’t magnetic which are susceptible to magnetism such as iron objects.  

Click on the interactive learning button (to the right of this section) to try a simulation that explores the magnetic field around a bar magnet using a compass. Remember compasses are really small free moving bar magnets. What you are seeing in this exploration is the interaction between two magnetic fields. Magnetism is more important than the magnetic stickers on the fridge or toys and torches.

Electromagnets

Magnetic effects can be easily produced by direct electric current flowing through a circuit and greatly amplified in intensity by the addition of an iron core that is surrounded by an electric current carrying coil. In fact the strongest magnets are always electromagnets. Because a conductor carrying an electric current has a magnetic field surrounding the coil that can be attracted or repelled by a magnetic field from a magnet or electromagnet. This means that electricity flowing in a device such as a motor containing a magnet can cause movement.

Take a look at this video that describes how a current carrying wire can interact with a magnetic field to produce a device that is a motor transforming electrical energy into mechanical energy. This video may not be available through the NSW DEC network.

Electric motors

Think about all the devices you have encountered that contain a motor. These could include the electric toothbrush you used today, the electric fan, air conditioner, the vacuum cleaner, compressor in your fridge or the washing machine. If you live in the city you have probably travelled by electric train. Some of you may have a family car that is a hybrid and runs most of the time on an electrical motor. Electric motors are incredibly important. Without them industry, houses and cities would be a vastly different place.

To learn more about electric motors, their applications and magnetism you might like to explore this website.

Making an electric motor is a great fun activity. Take a look at this video that discusses how an electric motor works, its history and how to build a simple electric motor including some great tips to ensure you have success.

To explore how a direct current electric motor works go to the interactive learning guide and download the motor activity.