A circular coil A of radius r carries current I. Another circular coil B of radius 2r carries current of I. The magnetic fields at the centres of the circular coils are in the ratio of
Answer & explanation
Correct answer: option 4
$ \text{Magnetic Field due to circular coil is } B = \frac{\mu_0 I}{2r}$
$ \frac{B_1}{B_2} = \frac{r_2}{r_1} = 2$