The earth's magnetic field at a given point is `0.5xx10^(-5) Wb-m^(-2)`. This field is to be annulled by magnetic indcution at the centre of a circular conducting loop of radius `5.0 cm`. The current required to be flown in the loop is nearly

Options

A. 0.2 A
B. 0.4 A
C. `4 A`
D. `40 A `

Answer

B

Explanation

`B = (mu_(0) I)/(2 r) implies 0.5 xx 10^(-5) = (4pi xx 10^(-7) xx I)/(2 xx 5 xx 10^(-2))`
`implies I = (0.5 xx 10^(-6))/(4pi xx 10^(-7)) = 0.4 A`