99 Percentile Qs Bank for JEE MainPhysicsMagnetic Properties of Matter
A bar magnet of magnetic moment M is placed at a distance D with its axis along positive X -axis. Likewise, second bar magnet of magnetic moment M is placed at a distance 2 D on positive Y -axis and perpendicular to it as shown in the figure. The magnitude of magnetic field at the origin is B → = α μ 0 4 π M D 3 . The value of α must be (Assume D > > where l is the length of magnets)
Options
- A2
- B15 8
- C17 8
- D9 8
Correct answer
B. 15 8
Step-by-step solution
B axis = 2 μ 0 M 4 π D 3   &   B equator = μ 0 M 8 π D 3 since d = 2 D B net = B axis - B equator = μ 0 M 4 π D 3 2 - 1 8 ∴     B net = 15 8 μ 0 M 4 π D 3 ⇒ α = 15 8