Reduce or limit the current through the coils of the magnet. The strength of the magnetic field is related to the current flowing through the wire wound around the core of the magnet. If the current flow is reduced or limited, the strength of the magnet decreases. A cheap and easy component for limiting current is a simple resistor for homemade electromagnets..
Reduce the number of coils. Another factor in the strength of an electromagnet is the number of coils of wire wound around the core of the magnet. The greater the number of coils, the greater the strength of the magnetic field. Try removing turns of wire in order to weaken the electromagnet. Be careful not to nick the wire as many electromagnets are wound with a wire whose insulation is easily damaged.
Change the core material of the magnet. The composition of an electromagnet's core also affects how strong or weak it is. Magnets with cores made of iron will be much stronger than those with an air core; that is, a magnet wound on a form with no metallic core. To weaken the magnet, change the core from a metallic core to a non-metallic or air core.
- Use your imagination in trying to weaken the magnet. Try everything that pops into your mind, but rely on these steps for proven results.