Consider the current carrying loop shown in figure formed of radial lines and segments of circles whose centres are at point `P`. Find the magnitude and direction of B at point P.

Explanation

Magnetic field at `P` due to straight wires `=0`
Due to circular wires one is outwards (of radius a) and other is inwards`. 60^@` means `1/6` th of whole circle
`:.B=1/6[(mu_0i)/(2a)-(mu_0i)/(2b)]` (outwards)