1÷1 + (1 + 2 +)÷2 (1 +2 +3 )÷3 ...+ (1 + 2 + 3 ...n )÷n
A circular coil of radius 0.081m has 52 turns. It carries a current of 1.5A. What is the magnetic field on the axis of the coil at a distance equal to twice the radius of the coil? Also calculate the magnetic field at the centre of the coil.