Two concentric circular coils, each having 10 turns with radii 0.2 ~m and 0.4 ~m carry currents 0.2 ~A and 0.3 ~A respectively in opposite directions. Magnetic field at the centre is

Step-by-step solution

The magnetic field at the centre of a circular coil carrying current I is given by B= ₀ n I 2 R where, n = number of turns. For coil 1, B₁= ₀ 10 0.2 2 0.2 =5 ₀ For coil 2, B₂= ₀ 10 0.3 2 0.4 = 15 4 ₀ Net magnetic field, B=B₁-B₂=5 ₀- 15 4 ₀= 5 4 ₀