Making an Electromagnet

Aim

To make an electromagnet and study factors affecting its magnetic strength.

Materials Required

• Iron nail (soft iron)
• Insulated copper wire
• Battery (1-9V)
• Switch
• Iron pins or paper clips
• Connecting wires
• Magnetic compass

Theory

An electromagnet is a temporary magnet made by winding a coil of insulated wire around a soft iron core. When an electric current flows through the coil, it produces a magnetic field. The soft iron core gets magnetized by induction and greatly increases the strength of the magnetic field. When the current is switched off, the soft iron loses its magnetism almost immediately.

The strength of an electromagnet depends on:

1. Number of turns in the coil: Greater the number of turns, stronger is the magnetic field.
2. Magnitude of current: Greater the current (determined by voltage), stronger is the magnetic field.
3. Nature of core material: Soft iron produces a much stronger electromagnet than air or hard steel.

Procedure

1. Take a long iron nail and wind the insulated copper wire closely around it to form a coil.
2. Connect the free ends of the wire to a battery through a switch.
3. Place some iron pins or paper clips near the head or tip of the nail.
4. Switch ON the current and observe what happens to the pins.
5. Bring a magnetic compass near the nail to observe the magnetic field.
6. Vary the number of turns of wire and the voltage of the battery, and count the number of pins attracted in each case.
7. Switch OFF the current and observe what happens.

Precautions

• Use insulated copper wire to avoid short circuits.
• Do not keep the current ON for a long time as the wire will get heated up and may burn, and it will quickly drain the battery.
• Ensure the connections are tight.
• Use a soft iron core (like a standard nail), not steel, for temporary magnetism.