Pyq- Magnetostatics Introduction & Biot Savart Law

• NEET 2018:

The magnetic field at a point on the axis of a circular coil of radius R carrying a current I is given by

B = (mu_0 I)/(2pi x)

where x is the distance of the point from the centre of the coil.

The magnetic field at the centre of the coil is given by

B = (mu_0 I)/(2R)

So, the answer is (B).

• NEET 2017:

The magnetic field at a distance d from a long straight wire carrying a current I is given by

B = (mu_0 I)/(2pi d)

The field at a distance 2d is given by

B = (mu_0 I)/(2pi (2d)) = (mu_0 I)/(4pi d) = B/2

So, the answer is (A).