Two circular loop of radii 10 cm and 40 cm carries current of 1 A and 2 A respectively. Find the ratio of magnitude of magnetic field at their centres?

Answer 1

The magnetic field at the center of a current loop is proportional to I/R where I is the loop current and R is the loop radius.

The field in loop one is proportional to 1/10 and the field in loop two is proportional to 2/40.

The first loop's field is twice the second loop's field.