NEETPhysicsMagnetic Effects of Current
An insulating thin rod of length l has a linear charge density ρ x = ρ 0 x l on it. The rod is rotated about an axis passing through the origin x = 0 and perpendicular to the rod. If the rod makes n rotations per second, then the time averaged magnetic moment of the rod is:
Options
- Aπ 4 n ρ 0 l 3
- Bn ρ 0 l 3
- Cπ n ρ 0 l 3
- Dπ 3 n ρ 0 l 3
Correct answer
A. π 4 n ρ 0 l 3
Step-by-step solution
ω = 2 π n rad s - 1 d Q = ρ d x = ρ 0 l x d x Current due to elementary charge d Q d I = d Q ω 2 π Magnetic dipole moment d M = d I × A ∫ d M = ∫ 0 l ω 2 π × ρ 0 l × x d x π x 2 M = π n ρ 0 l 3 4