An are of a circle of a radius R subtends an angle `(pi)/(2)` at the centre .it carries a current l. The magnetic field at the centre will be

Options

A. `(mu_(0)I)/(2R)`
B. `(mu_(0)I)/(8R)`
C. `(mu_(0)I)/(4R)`
D. `(mu_(0)I)/(5R)`

Answer

B

Explanation

Magnetic field at the center of a circular are of radius R, carries current I and making an angle`phi` at the centre is given by
`B=(mu_(0)Iphi)/(4piR)`
In the given problem `phi=(pi)/(2)`
`phi=(pi)/(2)`
`:. B=(mu_(0)I(pi"/"2))/(4piR)=(mu_(0)I)/(8R)`