Variable coil electromagnet has 6 different coil options:100, 200, 300, 400, 500 and 600 coils. A hook underneath used to measure the strength of the magnetic field To study the effect of current and number of coils on the strength of an electromagnet. Tapping at 100, 200, 300, 400, 500, 600 turns. The weights used are large paper clips. A variable D.C. low voltage supply is required.