Concepts Of Physics MCQ Edition [Volume 2]PhysicsPermanent Magnets
Suppose r represents the distance of a point on the axis of a bar magnet from its centre. The magnetic field at this location is proportional to
Options
- A1 r^3
- Br (r^2 - l^2)^2 (where 2l is the magnet's length)
- C1 r
- D1 r^2
Correct answer
B. r (r^2 - l^2)^2 (where 2l is the magnet's length)
Step-by-step solution
The magnetic field due to a bar magnet of length 2l and magnetic dipole moment M at a point on its axial line at a distance r from the centre is given by B = ₀ 4 2Mr (r^2 - l^2)^2 Therefore, the magnetic field is proportional to r (r^2 - l^2)^2 .