Question

A long conducting wire having a current I flowing through it, is bent into a circular coil of N turns. Then it is bent into a circular coil of n turns. The magnetic field is calculated at the centre of coils in both the cases. The ratio of the magnetic field in first case to that of second case is 

(1) N : n 

(2) n² : N² 

(3) N² : n² 

(4) n : N

Answer 1

Correct option is (3) N² : n²