Physics · JEE | Magnetism and Matter

A small magnetized needle P of magnetic moment \( m \) is placed at a distance \( r \) on the axial line of another identical magnetized needle Q. The magnetic field \( B_A \) experienced by Q due to P is given by:

1. A
   \( \frac{\mu_0 m}{4\pi r^3} \)
2. B
   \( \frac{\mu_0 2m}{4\pi r^3} \)
3. C
   \( -\frac{\mu_0 m}{4\pi r^3} \)
4. D
   \( -\frac{\mu_0 2m}{4\pi r^3} \)