Question

A bar magnet has a magnetic moment of $2.5 J T ^ { - 1 }$ and is placed in a magnetic field of $0.2 T$ Work done in turning the magnet from parallel to anti-parallel position relative to field direction is

• A. 0.5 J
• B. $1 J$
• C. $2 J$
• D.

Answer 1

Answer: (B)

$1 J$

Answer 2

Work done, W$= - M B \left( \cos \theta _ { 2 } - \cos \theta _ { 1 } \right)$

$= 2 M B$

$= 2 \times 2.5 \times 0.2 = 1 J$