A simple electromagnet can be made by coiling an insulated wire around a large nail. The coil of wire can then be connected to the DC terminals of a variable 12V power supply. Two different independent variables can be investigated, the number of turns on the coil or the voltage connected across it. Both will affect the strength of the magnet.
- 50cm of insulated wire.
- Large nail.
- 12V power supply (set to 10V)
- Paper clip.
- 30 cm ruler.
- Wrap 10 coils of wire around the magnet and connect it to the power supply.
- Place the end of the magnet at the 0 cm and of the ruler.
- Turn on the magnet.
- Slowly push the paper clip along the ruler towards the magnet.
- Record the distance at which the paper clip is attracted towards the magnet.
- Turn off the magnet.
- Repeat this process with 15, 20, 25 and 30 turns.
- You may wish to repeat each test 3 times to calculate mean distances.
If the magnet is left turned on for more than 10 seconds or so the wire will get hot. This could cause a burn or even cause the insulation to melt. To avoid this only have the magnet turned on for a few seconds at a time. Take care when picking up the magnet remember it may be hot.