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

- 2
- 1/2
- 1
- 1/4

**Answer**

Magnetic field at the centre of the coil is given by

B = (μ_{o}NI)/(2R)

Since both current (numerator) and radius (denominator) are doubled, the magnetic field produced by coil A and B will be same. So, the ratio will be 1.

**The correct option is C.**