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

Answer

B

Explanation

The magnetic field at the centre of a circular loop carrying current I is given by `B=(m_0I)/(2r)`
where r is the radius of the circular loop .
Given that r = 5.0 cm = 0.5 m.
Now `B=(mu_0I)/(2r)=0.5xx10^(-5)`
`rArr I=(0.5xx10^(-5)xx2xx0.05)/(mu_0) = (0.5xx10^(-5)xx0.1)/(4pixx10^(-7))`
`= 0.3978 ~~0.4` Å