Question

The magnetic field strength at the center of a circular coil with N turns is B. If the number of turns is double but the current and radius are each half, the magnetic field strength at the center would be 

Answer 1

Answer

Magnetic field at center of coil is given

By

$B=\frac{N\mu_0 I}{2R}$

If

number of turns is double but the current and radius are each half

Then

magnetic field strength at the center would be

$B'=\frac{2*2N\mu_0 I}{2R}\\=4B$

Magnetic field become four times as earlier.