Question

A long straight conductor carrying current is placed near a current carrying circular loop as in the figure.

1. If B is the field of the ring and B the field due to straight conductor what will be the direction of B and B at O.

2. The current through the loop and the conductor are 2A and the conductor is at as distance 20 cm from the centre of loop. What should be the diameter of the loop so that the net field at O is zero.

Answer 1

1. B₁ into the plane and B₂ out of the plane.

2. B₁ is the field of the ring and B₂ the field of due to straight conductor.

B = B₁ – B₂ = 0

B₁ = B₂

_{\(\frac{\mu_0}{2}\frac{1}{a}=\frac{\mu_0}{2x}\frac{1}{d}\)}

_{\(\frac{a}{2a}\) = \(\frac{2}{2\times \pi\times 20\times10^-2}\)}

2a = 40π × 10^-2m = 1,256m

Diameter d = 1.256 m.