Alternating Magnetic Field with AC Current


To conduct a simple experiment to understand how AC current creates an alternating magnetic field.

Materials required:

  1. A light bulb, preferably an elongated one.
  2. A powerful magnet.


  1. Keep the bulb in a holder which is within your reach.
  2. Switch on the bulb.
  3. Bring the magnet near the light bulb and observe how the filament of the bulb starts wiggling and shaking inside the bulb.

Scientific explanation:

When an electric current passes through any conductor like a wire or a bulb filament, it creates a magnetic field. Just like a normal magnet, this magnetic field will also have a North Pole and South Pole. In the case of the light bulb, the current flowing through the filament is alternating current (AC) which is the type of electricity we get from the power supplies at our houses. In AC electricity flows in one direction and then switches and flows in the reverse direction. This happens 120 times a second. Each time the direction of current flow reverses, the direction of the magnetic field and the poles also reverses.

When you bring a permanent magnet near this alternating magnetic field, the filament of the bulb gets attracted and repelled alternately 120 times in every second. This causes the filament to shake and wiggle.