Question

When a Magnetic needle is suspended freely, it always aligns itself in the direction of magnetic north and south pole of the earth, the north pole of the needle gets attracted towards the magnetic south pole of the earth and the south gets repelled equally away from it. So two equal and opposite forces acting on the needle should cancel each other which does not happen because the:

• A. Force of attraction and repulsion are equal but not exactly in opposite direction
• B. Force of attraction and repulsion are not exactly equal even though in opposite direction
• C. Force of attraction and repulsion are not equal and not in opposite direction
• D. Force of attraction and repulsion are exactly equal and opposite in direction

Answer 1

Answer: (B)

Force of attraction and repulsion are not exactly equal even though in opposite direction

Though two equal and opposite forces are acting on the needles, they don't cancel each other as they act on two different points and they generate torque which later at proper alignment reaches equilibrium such as

$\sum F=0$ and

$\sum M=0$