Question

If in a circular coil A of radius R, current I is flowing and in another coil B of radius 2R a current 2I is flowing, then the ratio of the magnetic fields BA and BB, produced by them will be(a) 1(b) 2(c) $\frac{1}{2}$(d) 4

Answer 1

Answer:

A) 1

Explanation:

Radius of the circular coil A = r (Given)

Current of the circular coil A = l (Given)

Radius of the circular coil B = 2r (Given)

Current of the circular coil B = 2l (Given)

Magnetic field at centre of circular coil is given by - B = (μoNI)/(2R)

Thus, when i is kept constant  - B ∝ 1r

B₁B₂=r₂r₁

r₁ = r

r₂ = 2r

Since both the current (numerator) and the radius (denominator) are doubled, the magnetic field produced by coil A and B will be same. Thus, the ratio of the magnetic fields BA and BB, produced by them will be 1: 1