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My son is having a science project and we are trying to make and electro magnet to see if the electro magnet is stronger than the regular magnet. We need to know how to build a electro magnet and how big of a battery we will need.
- Dan Kernohan (age 35)
Harsens Island, MI. U.S.A.
There is a great explanation of exactly how to do this on the Bizarre Stuff: Fun with Electromagnets
website. They've got really good instructions, pictures, and
troubleshooting tips, but here's the basic part of what they say:
A basic electromagnet can be constructed around a long carriage bolt.
Almost any iron core will work, including a large nail, but the bolt is
simpler to work with. Screw a nut on to the end of the bolt so that
there are two stops on either end, the nut and the head of the bolt
itself. Wrap a piece of paper around the bolt between the nut and head
and tape in place. Leaving a foot or so free, coil an insulated wire
around the length of the bolt, between the head and the nut. Once the
end is reached, coil the wire back to the other end. Repeat until there
are several layers. The free ends of the wire should be at opposite
ends of the bolt. Tape the wire so that it stays in place. Leaving a
foot or so free, cut the wire off at the end. Strip the insulation off
the ends of the wires. When the wires are attached to a battery (dry
cell), the electric current around the wire and bolt will form a
magnetic field. Don't use it too long, as the battery will drain very
Hope this helps!
(republished on 08/02/06)
Follow-Up #1: Why paper in the bolt electromagnet?
What is the significance of the paper around the bolt? I have done this with just the bolt or nail and the wire but have never used the paper.
Does this effect the field direction?
- Alexander (age 12)
Akron, Ohio, USA
followup to #2376
The presence of the paper has nothing to do with the magnetic field. It's only purpose is to possibly prevent a short circuit between the wire and the bolt.
(published on 11/11/09)
Follow-up on this answer.