Electromagnets Target: to know how to make an electromagnet and test its strength. Wednesday 30 September 2009

Target:

to know how to make an electromagnet and test its strength.

Magnetic field around a straight conductor The magnetic field around a straight conductor has the shape of concentric circles. Notes

Electromagnets An electromagnet is a magnet that is made using an electric current. An electromagnet is made by wrapping wire around an iron core. The magnetic filed can be turned on or off. An example of an electromagnet is the magnet used in scrap yards to pick up cars. Notes

An electromagnet is a magnet that is made using an electric current.

An electromagnet is made by wrapping wire around an iron core.

The magnetic filed can be turned on or off.

An example of an electromagnet is the magnet used in scrap yards to pick up cars.

Make an electromagnet by wrapping wire around the iron core. Connect it to a 2V power supply and switch it on. Wrap the wire round 10 times See how many paper clips you can pick up Then add 10 more coils of wire Count how many paper clips you can pick up Then add 10 more coils Electromagnets Results table

Make an electromagnet by wrapping wire around the iron core. Connect it to a 2V power supply and switch it on.

Wrap the wire round 10 times

See how many paper clips you can pick up

Then add 10 more coils of wire

Count how many paper clips you can pick up

Then add 10 more coils

Remember to make it a fair test you must keep the current the same. Write an explanation of what your results show – if you have time draw a simple graph to illustrate your results. Number of coils Number of paper clips 10 20 30 40

Questions 1. Look at the diagram. Explain why the steel ball is attracted to the electromagnet when the switch is on. 2. Explain why using an electromagnet is not attracted to the steel ball when the switch is off. 3. Explain why a steel ball might be attracted to the electromagnet even when the electromagnet is off. 4. What could be done if the electromagnet is not strong enough to pick up the ball to make it stronger? 5. What would happen to the ball if the leads on the power supply were reversed?

Questions 1. Look at the diagram. Explain why using an electromagnet is the best way to pick up paperclips or pins. 2. Explain why using an electromagnet is not always the best way to pick up steel paperclips or pins. 3. Name the poles at X and Y on the electromagnet. Give a reason for you answer. 4. Explain why an electromagnet is stronger if an iron core is used. 5. What would happen to the compasses shown in the diagram if the leads were reversed on the power supply?