Question

A small coil of N turns has an effective area A and carries a current I. It is suspended in a horizontal magnetic field $\vec { B }$ such that its plane is perpendicular to $\vec { B }$. The work done in rotating it by $180 ^ { \circ }$ about the vertical axis is

• A. NAIB
• B. 2NAIB
• C. $2 \pi N A I B$
• D. $4 \pi N A I B$

Answer 1

Answer: (B)

2NAIB

Answer 2

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