At a distance of 10 cm from a long staright wire carrying a current I, the magnetic field is 0.04 T. At a distance of 40 cm from the wire, the magnetic field will be

Options

A. `0.01 T`
B. `0.04 T`
C. `0.16 T`
D. `0.02 T`

Answer

A

Explanation

Here `r_1 = 10cm = 0.1 m, r_2 = 40 cm = 0.4 m and B_1 = 0.04 T`
`:. B_2 = (B_1 r_1)/(0.4) = 0.01 T`