Currents through ABC and `A^'B^'C^'` is I, figure. What is the magnetic field at P? `BP=PB^'=r`. (Here `C^'B^'PBC` are collinear)

Options

A. `B=1/(4pi)(2I)/r`
B. `B=(mu_(0))/(4pi)((2I)/r)`
C. `B=(mu_(0))/(4pi)(I/r)`
D. zero

Answer

B

Explanation

`B_(P)=2xx(mu_(I))/(4pir)=(mu_(0)i)/(2pir)`