Background
An electromagnet is a temporary magnet. An electromagnet has a magnetic field created by electric current. Electricity and magnetism are closely related to each other. Wherever there is electricity, there is a magnetic field, and wherever there is magnetism, there is potential for an electric field. The field disappears when the current is turned off. Electromagnets are essential to the creation of electrical devices such as motors, generators, speakers, computers, and MRI machines. They are popularly recognized for their role in picking up and moving heavy magnetic objects like scrap iron.
Why do this in your classroom?
- To encourage the following process skills for scientific investigation: prediction, observation, developing a hypothesis, and drawing conclusions.
- To help students understand the relationship between electricity and magnetism.
- To allow students to manipulate variables and record changes.
Materials
- Battery (D or C)
- Copper wire (about 85 cm or more)
- Paper clips
- Iron rod
- Magnet
- Compass
Procedure
- Connect the copper wire to the ends of the battery to create a circuit. Now place the current carrying wire next to the compass. Do you notice any change?
- Ask the students to explain what happened. Although copper is not magnetic, the current flowing in the wire is. A magnetic field is being produced by the flow of electrons in the wire. That magnetic field produced can be used to magnetize a temporary magnet if the field was concentrated. Wrap the wire three times around the iron rod and connect it to the battery. This is a weak electromagnet. Show the students the magnets strength by trying to pick up paperclips on the iron rod. How many did you get?
- Have the students try to build a stronger electromagnet using the materials supplied and the concepts taught so far in the day. Pass out the materials and give the students time to work. If the students are struggling, suggest “adding more magnetism” to their electromagnet and ask them why their copper wire is so long.
- After all groups have finished constructing their magnets, bring them together and discuss the various successes of different groups. Compare and contrast the constructions of electromagnets of different strengths. There are several variable to strengthen the electromagnets. Let the students try a few ideas (number of batteries, more wire, neatness of the coil, temperature, etc…). The variables discussed should include battery strength, neatness of wire coiling, and number of coils. Ask each group what they could do to make their magnets stronger for the next time they would do this.
What’s happening?
By coiling a current carrying wire, you can concentrate the magnetic field in the center of the coil. The DC current from a battery will create a flow of electrons in the same direction. So the wire carrying a DC current will have a small magnetic field around it. Coiling the wire concentrates the magnetic field inside the coil. Whatever is placed inside this coil will then be in a stronger magnetic field than if the wire was uncoiled.
For more information contact MagLab educator Carlos R. Villa.
