A short bar magnet placed with its axis at 30° with an external field of 800 G experiences a torque of 0.016 Nm. The magnetic moment of the magnet is, the work done in moving it from its most stable to most unstable position is that

Question

A short bar magnet placed with its axis at 30° with an external field of 800 G experiences a torque of 0.016 Nm. The magnetic moment of the magnet is, the work done in moving it from its most stable to most unstable position is that (A) 0.064 J (B) 0.024 J (C) 0.01 J (D) 3.2 J

Tardigrade Admin · Accepted Answer

The most stable position is θ=0° and the most unstable position is θ=180°, work done is given by W =Um(θ=180°)-Um(θ=0°) ⇒ =2 m B=2 × 0.40 × 800 × 10-4 =0.064 J

Q. A short bar magnet placed with its axis at $3 0^{\circ}$ with an external field of $800 G$ experiences a torque of $0.016 N m$ . The magnetic moment of the magnet is, the work done in moving it from its most stable to most unstable position is that

0.064 J

0.024 J

0.01 J

3.2 J

The most stable position is $θ = 0^{\circ}$ and the most unstable position is $θ = 18 0^{\circ}$ , work done is given by
$W = U_{m} (θ = 18 0^{\circ}) - U_{m} (θ = 0^{\circ})$
$\Rightarrow= 2 m B = 2 \times 0.40 \times 800 \times 1 0^{- 4}$
$= 0.064 J$

Q. A short bar magnet placed with its axis at 30∘ with an external field of 800G experiences a torque of 0.016Nm. The magnetic moment of the magnet is, the work done in moving it from its most stable to most unstable position is that