Two circular coil of radii 5cm and 10cm carry equal currents of 2A. The coils have 50 and 100 turns, respectively, and are placed in such a way that their planes as well as their centers coincide. Magnitude of magnetic field at the common centre of coils is

Options

A. `8pixx10^(-4)T` if current in the coil are in same sense.
B. `4pixx10^(-4)T` if current in the coil are in opposite sense.
C. Zero if currents in the coils are in opposite sense.
D. `8pixx10^(-4)T` if current in the coil are in opposite sense.

Answer

A,C

Explanation

`B_(1)=(mu_(0)N_(1)I)/(2r_(1))+(mu_(0)N_(2)I)/(2r_(2))`
`=8000pixx10^(-7)=8pixx10^(-4)T`