Question

The magnetic field of a given length of wire for a single turn coil at its center is 'B' its value for a turn coil for the same wire is :

• A. $\frac{B}{4}$
• B. $\frac{B}{2}$
• C. 4B
• D. 2B

Answer 1

Answer: (C)

4B

Answer 2

The correct option is (C): 4B

B1 = B = $\frac{\mu I_0}{2R}$
B2 = $\frac{\mu_0(2I)}{2r}$
$\therefore$ 2 × 2πr = 4πR ∴ r = $\frac{R}{2}$ ∵ 2×2πr=4πR ∴ r=$\frac{R}{2}$