Figure shows three cases: in all case the circular part has radius r and straight ones are infinitely long. For the same current the ratio of field B at centre P in the three case `B_1:B_2:B_3` is

Options

A. `(-(pi)/(2)):((pi)/(2)):((3pi)/(4)-(1)/(2))`
B. `(-(pi)/(2)+1):((pi)/(2)+1):((3pi)/(4)-(1)/(2))`
C. `-(pi)/(2):(pi)/(2):3(pi)/(4)`
D. `(-(pi)/(2)-1):((pi)/(2)-(1)/(4)):((3pi)/(4)+(1)/(2))

Answer

A