Question

The magnetic moment of a current carrying loop is $2.1\times {10}^{-25}$ $amp\times m^2$. The magnetic field at a point on its axis at a distance of $1A^o$ is

• A. ${4.2\times 10}^{-2}weber/m^2$
• B. ${4.2\times 10}^{-3}weber/m^2$
• C. ${4.2\times 10}^{-4}weber/m^2$
• D. ${4.2\times 10}^{-5}weber/m^2$

Answer 1

The correct option is A ${4.2\times 10}^{-2}weber/m^2$

Field at a point $x$ from the centre of a current carrying loop on the axis is

$B=\frac{{\mu }_0}{4\pi }.\frac{2M}{x^3}$

$=\frac{{10}^{-7}\times 2\times 2.1\times {10}^{-25}}{({10}^{-10}{)}^3}$

$=4.2\times {10}^{-32}\times {10}^{30}$

$=4.2\times {10}^{-2}W/m^2$