Question

A wire of fixed length is turned to form a coil of one turn. It is again turned to form a coil of four turns. If in both cases same amount of current is passed, then the ratio of the intensities of magnetic field produced at the center of a coil will be

• A. 16 times of first case
• B. $\frac{1}{9}$ times of first case
• C. 4 times of first case
• D. $\frac{1}{3}$ times of first case

Answer 1

The correct option is A

16 times of first case

Magnetic field at the centre of n turn coil carrying current i $B=\frac{{\mu }_0}{4\pi }.\frac{2\pi ni}{r}.B\alpha \frac{n}{r}$ and nr = constant .