Question

A wire of length l carrying i is bent into a circle .The magnitude of the magnetic feild at the centre of the circle is

Answer 1

As we learnt in

Magnetic moment (M) -

M=NiA

- wherein

N-number of turns in the coil

i-current throughout the coil

A-area of the coil

Magnetic moment \vec{\mu }=I\vec{A}

=I.\pi r^{2}=I.\pi(\frac{L}{2\pi})^{2}

=\frac{IL^{2}}{4\pi}

Option 1)

\frac{IL}{4\pi}

incorrect

Option 2)

\frac{IL^{2}}{4\pi}

correct

Option 3)

\frac{I^{2}L^{2}}{4\pi}

incorrect

Option 4)

\frac{I^{2}L}{4\pi}

incorrect