Question

Which of the following shows that the earth behaves as a magnet ?

• A. Repulsion between like poles
• B. Attraction between unlike poles
• C. Existence of null points in the magnetic field of a bar magnet
• D. Non-existence of monopoles

Answer 1

The correct option is C Existence of null points in the magnetic field of a bar magnet

Answer is C.

Null points exist where the field due to the magnet is equal and opposite to the horizontal component of the earth's field.
At the two points marked X in figure, the earth's magnetic field and the magnet's field are exactly equal and opposite and the resultant field is zero. These points are called the null or neutral points.
Figure (a) and (b) shown below illustrate the null points when the magnet is placed in two different positions.
Hence, this proves that the earth behaves like a bar magnet.