A circular segment of radius 10 cm, subtends an angle of 60° at its centre. A current of 9 ampere is flowing through it. Find the magnitude and direction of the magnetic field produced at the centre. 

Here, r = 10cm = 0.1m, θ = 60°, I = 9A, B = ? 

Here CD is the circular segment with centre O, in the plane of paper figure. 

Let I = length of the segment CD. It subtends an angle 60° 

(- π/3) at O i.e., α = π/3 rad.

Magnetic field induction at O due to current through segment CD will be 

            The direction of magnetic field induction, according to Right Hand Rule will be downwards perpendicular to the plane of paper.