Question

A wire of length L metre carrying a current of I ampere is bent in the form of a circle. Its magnitude of magnetic moment will be equal to?

• A. $\frac{IL}{4\pi }$
  
• B. $\frac{I{L}^2}{4\pi }$
  
• C. $\frac{I^2{L}^2}{4\pi }$
  
• D. $\frac{I^{2}L}{4\pi }$

Answer 1

The correct option is B $\frac{I{L}^2}{4\pi }$


If the radius of circle is r, then $2\pi r=L\Rightarrow r=\frac{L}{2\pi }$
Area $=\pi r^2=\frac{\pi L^2}{4{\pi }^2}=\frac{L^2}{4\pi }$
Magnetic moment $=IA=\frac{I{L}^2}{4\pi }$