NEET2016PhysicsMagnetic Effects of CurrentActual
A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60 o is W . Now, the torque required to keep the magnet in this new position is
Options
- AW 3
- B3 W
- C3 W 2
- D2 W 3
Correct answer
B. 3 W
Step-by-step solution
W = P E cos ⁡ θ 1 - cos ⁡ θ 2 W = P E cos ⁡ 0 - cos ⁡ 60 o = P E 2 . ⇒ P E = 2 W τ = P E sin ⁡ θ = 2 W sin ⁡ 60 o = 3 W .