A cool science experiment which teaches kids about a magnetic field is to make an electromagnet from scratch. Electromagnet principles and theory was developed by Andre Marie Ampere in 1821. D.F. Arago then invented the first working electromagnet. This invention helped lead Michael Faraday to later invent the electric motor.
- Magnet wire (about 5-10 feet)
- Iron nail
- Metal paper clips
- Battery (D cell or lantern battery) with battery holder or connection wires
Step 1: First, an iron or steel nail is needed. Do not use a galvanized or aluminum nail or the required magnetic field is not created. Leaving approximately 6" of wire slack, start wrapping the magnet wire around the iron nail.
Step 2: Wrap the wire 25 times around the nail.
Step 3: Attach both ends of the loose wire to the battery. Connect one side to the positive (+) side and the other side to the negative (-) side. Do not leave the wire attached to both battery terminals too long or the battery power will be drained and the wire will get hot.
Step 4: Move the nail near the paper clips.
Step 5: Disconnect one side of the wire from the battery.
Step 6: Wrap the wire another 25 turns around the nail.
The electromagnet proves that a magnetic field and electricity are related. In fact, calculation of electromotive force is very similar to Ohm's law. Remember that Ohm's law is used to calculate the voltage drop across a circuit with a resistor, where v=iR (voltage=current x resistance). To calulcate the electromotive force in a magnetic circuit use the equation F=IN (Force=current x number of turns). The number of turns and the current in the battery both change the amount of magnetic force in an electromagnet.