Question

A bar magnet with a magnetic moment 50 $Am ^2$ is placed in parallel position relative to a magnetic field of 0.4T. The amount of required work done in turning the magnet from parallel to antiparallel position relative to the field direction is

• A. $4 J$
• B. $1 J$
• C. $2 J$
• D. Zero

Answer 1

Answer: (A)

$4 J$

Answer 2

$u=−MBcosθ$

$W=Δu$

$W=−MBcos180^0(−mBcos0^0)$

$W=2MB$

$W=2×5×0.4$

$W=4J$

Therefore, the correct answer is (A): 4J