A steady current flows in a long wire. It is bent into a circular lopp of one turn and the magnetic field at the centre of the coil is B. If the same wire is bent into a circular loop of n turns, the magnetic field at the centre of the coil is

Options

A. `B/n`
B. `nB`
C. `Nb^(2)`
D. `n^(2)B`

Answer

D

Explanation

The magnetic field of circular coil, `B=(mu_(0)ni)/(2r)`
`Bpropn/r`
`impliesB_(1)/(B_(2))=(n_(1))/(n_(2))xx(r_2)/(r_(1))`
`implies(B)/(B_(2))=1/n.1/n`
`thereforeB_(2)=n^(2)B`