Assertion: magnetic field due to a infinite straight conductor varies inversely as the distance from it.
Reason: the magnetic field at the centre of the circular coil is zero

Options

A. If both the assertion and reason are true and reason is a true explantion of the assertion.
B. If both the assertion and reason are true but the reason is not the correct explantion of the assertion.
C. If assertion is true but reason false.
D. If asseration and reason both are false.

Answer

B

Explanation

The magnetic field at a point due to current flowing thorugh an infinitely long conductor is given by
`B = (mu_(0))/(4pi), (2l)/(a)`
where, `a` is the distance of that from conductor. Now accroding to right hand thumb rule in follows that magnetic field is in the form of concentric circles, whose centres lie on the straight conductor (but opposite in direction) my symbol.