Question

If in a circular coil A of radius R, current $i$ is flowing and in another coil B of radius 2R a current $2i$ is flowing, then the ratio of the magnetic fields, ${{B}_{A}}$ and ${{B}_{B}}$ produced by them will be:

• A. 1
• B. 2
• C. 44563
• D. 4

Answer 1

Answer: (A)

1

Answer 2

Magnetic field in circular coil A is Similarly ${{B}_{A}}=\frac{{{\mu }_{0}}Ni}{2R}$ R is radius and i is current flowing in coil. ${{B}_{B}}=\frac{{{\mu }_{0}}N(2i)}{2.(2R)}$ $=\frac{{{\mu }_{0}}Ni}{2R}$ $\frac{{{B}_{A}}}{{{B}_{B}}}=\frac{1}{1}=1$