How to Test the Strength of an Electromagnet
Electromagnets work by converting an electrical current into a magnetic field. The stronger the current passed through the electromagnet's coils, the stronger the magnetic field they will produce and the greater the force they will exert on most metal objects.
You can take advantage of the magnet's pull on metal object to get test the magnet's strength. If your electromagnet can run at various voltage settings you will have to test its strength on each setting, as it will vary with voltage.
Use a small knife to strip about one centimetre of insulation off the ends of your copper wire, if it is insulated. Connect the wire to both ends of the electromagnet, either by wrapping it tightly around the magnet or by taping it in place.
Select some small metallic objects. Non-plastic coated paper clips and small washers work well. Pile the objects you choose on a nonmetallic surface.
Turn your electromagnet on and dangle one of the end of copper wire into the pile of metallic objects. You can wave the wire gently back and forth until you are sure that it has collected as many objects as possible. Carefully move the wire away from the pile, turn off the electromagnet and allow the objects to drop away.
Weigh the objects that the magnet was able to pick up. The more accurate your scale, the more accurate the assessment of your magnet's strength.
Repeat steps three and four at least five times. Keep a record for the exact weight the magnet was able to collect in a table. After you are satisfied that you are receiving consistent results with each test, find an average weight that the magnet was able to lift.