Question

You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper wire and a switch. Label the poles of the electromagnet.

Answer 1

Hint: We will discuss how to arrange the given materials to get an electromagnet. After that we will use our theoretical knowledge to tell about which of the sides of the electromagnet will be the north pole. We will check on the direction of magnetic field lines using the right hand rule and accordingly designate the poles of the electromagnet.

Complete step by step answer:
We will connect the coil of copper wire to the cell with a switch in between to turn the electromagnet on and off. When the current will pass through the coil, we will also insert the bar of soft iron inside the coil. By doing this we will get a strong electromagnet that we can switch on and off when we want.

This is what the setup will look like when we have connected everything. Now as we know the current will flow from the positive terminal of the battery to the negative terminal in doing so it will pass from the bottom end of the coil to the top end. To get the direction of magnetic field lines, we will use the right hand thumb rule. We will curl the fingers of our right hand in the direction of current flow and our thumb will point in the same direction as magnetic field lines. Here the thumb will point in the upward direction. Magnetic field lines come out at the north pole. So in our setup the top side will be the north pole and the bottom side the south pole.

Note: Students must know that even if we don’t put the soft iron bar inside the insulated copper coil, it will still act as an electromagnet. But the electromagnet produced that way would be very weak. Putting a soft iron core(bar) inside the coil, increases the strength of the electromagnet many times.