Question

Two circular coils are made up of identical wires of length 30 cm. The number of turns in one coil is 5 and the number of turns in the other is 10. Find out the ratio of magnetic induction at the center of each coil when the same current flows through them:

• A. 2:1
• B. 1:2
• C. 4:1
• D. 1:4

Answer 1

The correct option is D 1:4

magnetic induction at the center of each coil $B=k{n}^2$ where n is number of turns.

The ratio becomes $\frac{B_1}{B_2}=\frac{k\left(5^2\right)}{k\left({10}^2\right)}=1:4$