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- Thin wire
- A long nail = 10p is a good size (10P = 10-penny - 3-inches, the size of the nail *)
- Two 1.5 volt D-cell batteries, AND/OR a 12-volt lantern battery
- Wire cutter
- Masking tape
- A "knife" switch – you should be able to find this in a hobby shop, electronic supply or a hardware store. Get a DC (direct current) switch **
- Electrical tape
- Some paper clips
Wrap the wire that has been stripped bare very tightly around the nail - at least 50 times. Cut the wire leaving a few inches of wire at each end.
Tape down the end of the wire from the top of the nail to the negative pole of the battery. Make sure the wire is touching the battery end.
Open the knife switch and connect the wire from the bottom end of the nail to the terminal on the knife switch.
Cut another short piece of wire and tape the wire to the positive pole of the battery.
connect the wire from the battery to other terminals on the knife switch.
Close the circuit by closing the knife switch. When you do that, you create a circuit of electricity that passes through the wire round around the nail.
Touch the point of the nail to a couple of paper clips and watch what happens.
When the electric current passes through the wire round around the nail, it creates a magnetic field that reaches out in expanding circles. When a wire carrying electricity is twisted into a coil, it is called a solenoid. The magnetic field twists with the coiled wire, causing the magnetic field lines to concentrate inside the coil. This creates a powerful magnetic effect inside the coil called an electromagnet.
The magnetic field inside the coil causes the tiny magnetic fields in the metal of the nail to be aligned in one direction (all the north poles point the same way). These little fields all pointing in the same direction add to the coil and make the magnet strong enough to pick up some objects.
How many paper clips can you pick up by the electromagnet? What would happen if you used two batteries and connected them together (make sure you connect the positive to the negative poles if you're using the two batteries)? Try to see how many paper clips you can pick up. Now, try using the nine-volt battery. (Connect the positive and negative terminals like on the regular batteries.) How many paper clips can you pick up? Is there any relationship between the voltage of the batteries and the number of clips you can pick up?
* WHAT DOES "PENNY" NAIL MEAN? The term penny (like 10p) originated in England many years ago. Ten penny, four penny, etc., nails got their names from the fact that one hundred nails of that size cost ten pence, four pence, etc. Today penny represents the definite length of a nail measured from the head to the tip of the point. The term penny is still shown by using the English Pence sign p.
** An inexpensive ($2.99) knife switch can be found at Radio Shack (Catalog #: 275-1537) with screw terminals and for low-power use.
