An infinitely long wire is bent in the form of a semicircle at the end as shown in the figure. It carries current I along abcdo. If radius of the semicircle be R, then the magnetic field at 'O' which is the centre of the circular part is

Options

A. A) `(mu_0 )/( 4 pi ) (2I)/( R ) ( pi +1)`
B. B) `(mu_0 )/( 4pi ) (2I)/(R ) ( pi -1)`
C. C) `(mu_0 )/( 4 pi ) (1)/(R ) ( pi +1)`
D. D) `(mu_0 )/( 4 pi) (1)/(R ) ( pi -1)`

Answer

C