Question

A thin insulated wire forms a plane spiral of N = 100 tight turns carrying a current 1 = 8 m A (milli ampere). The radii of inside and outside turns are a = 50 mm and b = 100 mm respectively. The magnetic induction at the center of the spiral is

(a) 5 μT 

(b) 7 μT 

(c) 8 μT 

(d) 10 μT

Answer 1

Correct answer is (b) 7 μT