Question

How could you prove that an electric current produces a magnetic field?

Answer 1

Perform the following experiment to show that an electric current produces a magnetic field.

Explanation:

Place several magnetic compass needles in a circle, around a conducting wire which can carry current. Provide a switch so that the current through the wire can be switched on and off. See picture below.

As seen in picture (a), when there is no flow of current through the wire, all the compass needles point in the Earth's North pole direction.

Now switch on a strong current `I` in the wire. As shown in the picture (b), each compass needle aligns in a direction which is tangential to the circle at respective point of location. If current is switched off, the state as shown in picture (a) returns.

The direction of such a magnetic field `B` is given by the right hand grip rule. Place your right hand with fist closed such that the thumb points towards the flow of current. The direction of the magnetic field is given by the direction of the closing fingers of hand. Also shown with red lines.