An electromagnet is a magnet made using electricity, thus it is only magnetic when there is electric current passing through the coil of wire. The direction of the north and south poles of an electromagnet depends on which way the current is flowing through the wires. You can increase the strength of an electromagnet by:
- increasing the number of coils
- increasing the current in the wire
- using a magnetic material for the core
So, make sure the materials below are all available and ready when you do this experiment in your science laboratory. Although this can be done individually, it is always better to do laboratory practicals in group to make sure the process could become interactive too amongst the group members.
You are going to make 5 electromagnets of different strengths, and in this practical vary the number of coils around the iron core.
Insulated wire for each group, at least 5 meters
alligator clips/crocodile clips
variable power supply (preferably 0v-15v range, DC)
small nails, paper clips (to test the strength of the electromagnet)
5-inch iron rod (at least 1 cm diameter, large nails could be a substitute)
To start with, make an electromagnet with 10 coils by winding an insulated wire around the iron core. Make sure you leave at least 5cm of wire to both ends to connect the power supply later on in the testing.
Put it aside, and make 4 more electromagnets with 30, 40, 60, and 80 coils.
To test the strength of your electromagnets, make a circuit connecting your electromagnet to a 6.0V power supply. You may also connect a galvanometer or milliammeter in series to your load, to check the current.
Put small nails on the table and pick them up using your electromagnet. Count the number of nails it is able to hold.
Record it in the suggested table below:
|No. of coils|| |
Number of Nails
Test the other electromagnets and record your results in the table.
Note: You must ask the kids to make their own conclusions. Let them suggest another method to increase the strength of the electromagnet. On the analysis part, ask them to graph results and let them identify the dependent and independent variables of the experiment.