Question

The strength of magnetic field at the centre of circular coil is

Answer 1

Answer:

answer.C

Explanation:

magnetic field due to two semi infinite wires =2(ui/4pi×r)=ui/2pi×r (outward)

magnetic field due to loop=ui/2r (inwards)

B at centre=ui/2r[1-1/pi]

Answer 2

For the given figure,

The strength of the magnetic field at the center of the circular coil can be calculated by=

The magnetic field at the center of the circular coil due to the circular portion-magnetic field at the center of the circular coil due to the straight portion.

Field due to the circular portion at the center= $\frac{\mu I}{2R}$(inwards)

Field due to the straight portion at the center= $\frac{\mu I}{2\pi R}$(outwards)

Hence, the strength of the magnetic field would be:

$\frac{\mu I}{2R}-\frac{\mu I}{2\pi R}=\frac{\mu I}{2R} (1-\frac{1}{\pi} )$

Hence, the correct option is (c).