A bar magnet of magnetic moment 104 J / T is free to rotate in a horizontal plane. The work done in rotating the magnet slowly from a direction parallel to a horizontal magnetic field of 4 × 10-5 T to a direction of 60° from the field will be

Question

A bar magnet of magnetic moment 104 J / T is free to rotate in a horizontal plane. The work done in rotating the magnet slowly from a direction parallel to a horizontal magnetic field of 4 × 10-5 T to a direction of 60° from the field will be (A) 0.2 J (B) 2 J (C) 4.18 J (D) 2× 102 J

Tardigrade Admin · Accepted Answer

Magnetic moment =104 J / T B=4 × 10-5 T, θ=60° Work done in moving the magnet in uniform magnetic field. W =M B(1- cos θ) =104 × 4 × 10-5(1- cos 60°) =0.2 J

Q. A bar magnet of magnetic moment $1 0^{4} J / T$ is free to rotate in a horizontal plane. The work done in rotating the magnet slowly from a direction parallel to a horizontal magnetic field of $4 \times 1 0^{- 5} T$ to a direction of $6 0^{\circ}$ from the field will be

$0.2 J$

$2 J$

$4.18 J$

$2 \times 10^{2} J$

Magnetic moment $= 1 0^{4} J / T$
$B = 4 \times 1 0^{- 5} T, θ = 6 0^{\circ}$
Work done in moving the magnet in uniform magnetic field.
$W = MB (1 - cos θ)$
$= 1 0^{4} \times 4 \times 1 0^{- 5} (1 - cos 6 0^{\circ})$
$= 0.2 J$

Q. A bar magnet of magnetic moment 104J/T is free to rotate in a horizontal plane. The work done in rotating the magnet slowly from a direction parallel to a horizontal magnetic field of 4×10−5T to a direction of 60∘ from the field will be

0.2J

2J

4.18J

2×102J