Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Move along the Magnetic Field Lines


To study the movement of a magnetic pole along the magnetic lines of forces.


Magnetic field is the magnetising force of a magnet. It is strongest near the poles of a magnet. If a magnetic material is placed in a magnetic field of a magnet, it is influenced by the force of the magnetic field. We can trace the lines of force of the magnetic field by using a small compass needle and a bar magnet.


bar magnet, needle, plastic tub, pieces of thermocol, glass


Near the wall of tub of water, put an inverted glass (after filling water in it) and lay the bar magnet over the glass. The magnet should remain above the water level.

Rub a pole of the magnet across a needle to magnetize it. Push this needle through a slice of thermocol. When put to float, the needle eye should remain above the water.

If the eye is the needle's north pole and you let it float near the north pole of the bar magnet, it starts moving along the magnetic lines of forces to reach the south pole.

Release the needle from different point near the north pole of the magnet, it travels along different lines.


The needle moves faster near the poles and slows down as the distance increases. The strongest field is at the poles of a magnet.


This experiment need verification.