Question

The magnetic field $B$ at point $P$ at a distance $R$ due to the wire of finite length carrying current $I$ is

• A. $\frac{{\mu }_o}{4\pi }\frac{I}{R}$
• B. $\frac{{\mu }_o}{2\pi }\frac{I}{R}$
• C. $\frac{{\mu }_o}{2\pi }\frac{2I}{R}$
• D. None of these

Answer 1

The correct option is B $\frac{{\mu }_o}{2\pi }\frac{I}{R}$

The magnetic field B at point P at a distance R due to a carrying current $I$ is :

$B=\frac{{\mu }_{o}I}{4\pi R}(sin\alpha +sin\beta )$

For infinite long wire,

$sin\alpha =sin\beta =1$

$\therefore B=\frac{{\mu }_{o}I\times 2}{4\pi R}$

$B=\frac{{\mu }_o}{2\pi }\frac{I}{R}$