### Magnetic Effects Of Current Question 18

#### Question 18 - 31 January - Shift 1

A bar magnet with a magnetic moment $5.0 Am^{2}$ is placed in parallel position relative to a magnetic field of $0.4 T$. The amount of required work done in turning the magnet form parallel to antiparallel position relative to the field direction is

(1) $4 J$

(2) $1 J$

(3) $2 J$

(4) Zero

## Show Answer

#### Answer: (1)

#### Solution:

#### Formula: Potential Energy Of A Magnetic Dipole

$u=-MB \cos \theta$

$W=\Delta u$

$W=-MB \cos 180^{\circ}(-mB \cos 0^{\circ})$

$W=2 MB=2 \times 5 \times 0.4=4 J$

Option 1