# Build and use an electromagnet

#### Due Feb 10, at noon

This project may be done by teams of 1-2 individuals. The idea is to create an electromagnet, and then to figure out the dependence of the magnet's strength on the number of coils of wire around it.

You can make an electromagnet by wrapping wire around an iron (or nickel or cobalt) rod: small cylindrical items such as screwdrivers, portable radio antennas, pointers, nails or screws will all do the trick. Wrap wire around the rod, then connect the ends of the wire to a battery. When current runs through the wire, it induces a magnetic field in the rod.

Task I Create an electromagnet. Verify that it will lift at least one paperclip. Describe your electromagnet, and draw a picture of it.

Task II Investigate the effect of different numbers of turns of wire around the rod. Use the same wire, but wrap varying amounts of it around the rod. Try to change the angle of the coils so that they always start at one end of the rod and terminate near the other. Make at least 4 different arrangements of wire, varying the number of coils by at least a factor of 10 from smallest to largest. For each arrangement, record the number of coils, and the largest number of paper clips the magnet can lift. The orientation of the paper clips might be important -- that is, whether you link them together into a chain first, or if you just try to stick a bunch directly onto the magnet. Which arrangement is easier for the electromagnet to lift? You may break some paper clips into fractions in order to increase the precision of your measurements.

Plot the maximum lifted weight against the number of coils. Is there any relationship? What relationship might you expect?

If you discover any surprising facts during the experiment, tell me about them.