Question

Magnetic field at the centre of a circular coil is B. Calculate the magnetic field at the same point when each of the current, number of turns of the coil and its radius is doubled.

Answer 1

Magnetic field at the centre of a circular coil having N turns in B = `(mu_0NI)/(2r)`

If I' = 2I, N' = 2N and r' = 2r

New magnetic field,

B' = `(mu_0N'I')/((2r')`

Then B' = `(mu_0(2N)(2I))/(2(2r))`

= `2*(mu_0NI)/(2r)`

= 2B

∴ The magnetic field also gets doubled.