How to Build a Powerful Electromagnet

Broadcast towers use extremely powerful electromagnets.

An electromagnet is made by wrapping a continuous strand of wire around a magnetic core. When current flows through the wire, it creates a magnetic field. Although the magnetic field is weak in a straight strand of wire, each turn of a wire coil increases the force, creating a strong, unified magnetic field. The more densely wrapped the wire, the better the core, and the more electricity flowing through the electromagnet, the more powerful it is.

Things You'll Need

• Magnetic core
• 22-gauge copper wire
• Tape
• Glue
• Scissors
• Power supply
• Lead-core solder
• Soldering iron
• Electrical tape

Instructions

1. Buy a core for your magnet. A large iron bolt or nail will create a powerful magnet, but a ferrite rod will do a better job focusing the magnetic field generated by the electric current.

2. Beginning at one end of the core, wrap 22-gauge insulated copper wire as tightly as possible to the other end, leaving at least 30 inches trailing off the first end. Tape or glue the wire at both ends of the core to prevent it from slipping off.

3. Loop the wire back to the starting point and wrap it a second time in the same direction as around the first wrapping. This will increase the magnetic field strength.

4. Wrap the magnet in tape to hold both wrappings firmly in place. Cut the wire free from the spool, leaving about 30 inches free at the far end.

5. Strip off about 1/2" of insulation from each end of the wire.

6. Attach the electromagnet to an adjustable DC power supply by soldering the wire ends to the terminals. Cover the exposed terminals by wrapping them in electric tape or some other insulating material.

7. Move the electromagnet as far away as possible from the DC power supply and any other metal items. Alternately, you may tape it to the power supply. The important thing is that it does not fly and hit the power supply, or pull nearby pieces of iron flying towards it unexpectedly when it is turned on.

8. Turn on the DC power supply to about 3 volts of power. Gradually increase the voltage until the electromagnet begins to get hot. Decrease the voltage until the magnet is cool enough to handle. This is the maximum power of the electromagnet.

Tips & Warnings

• Do not touch the contacts of the power supply when it is turned on or operate the electromagnet with the contacts exposed. Even at relatively low voltages, a power supply can produce dangerous amperage, potentially causing injury or death.

• Do not let kids build this magnet or use it unsupervised.

References

• Jefferson Lab: How do I Make an Electromagnet?
• Sciencenetlinks.com: Build an Electromagnet
• Nasa's Kids Science News Network: Does an Electromagnet Work Like a Regular Magnet?

Resources

• Ferrite Rods