Question

The magnitude of a magnetic field at the centre of a circular coil of radius R, having N turns and carrying a current I can be doubled by changing

• A. I to 2I and N to 2N keeping R unchanged
• B. N to N/2 and keeping I and R unchanged
• C. N to 2N and R to 2R keeping I unchanged
• D. R to 2R and I to 2I keeping N unchanged
• E. I to 2I and keeping N and R unchanged

Answer 1

Answer: (E)

$\because$ Magnetic field due to circular current carrying coil, $B=\frac{\mu_{0} N I}{2 r}$
$B$ can be doubled by changing $I$ to $2 I$ and Keeping $N$ and $R$ unchanged.