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COMEDK · Physics · 20. Magnetic Properties of Matter

On both sides of a magnetic needle, two short magnets A and B are placed on the same horizontal line which is perpendicular to the magnetic meridian. The south poles of A and B are facing each other, which are 10 cm and 20 cm respectively from the magnetic needle. If the needle remains undeflected, the ratio of the magnetic moment of A to that B is:

  1. A \(2:1\)
  2. B \(1:2\)
  3. C \(8:1\)
  4. D \(1:8\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(1:8\)

Step-by-step Solution

Detailed explanation

The magnetic field due to a short magnet on its axial line at a distance \(d\) is given by \(B = \dfrac{\mu_0}{4\pi} \dfrac{2M}{d^3}\). Since the magnetic needle remains undeflected, the magnetic fields produced by magnets A and B at the position of the needle must be equal and…