As shown in the figure two infinitely long, identical wires are bent by `90^(@)` and placed in such a way that the segments LP and QM are along the x-axis , while segments PS and QN are parallel to the Y-axis If OP=OQ=4 cm ,and the magnitude of the magnetic field at O is `10^(-4)` T, and the magnitude of the current in each wire and the direction of the magnetic field at O will be
`(mu _(o) =4pi xx10-7NA^(-2)):`

Options

A. 40 A, perpendicular into the page
B. 20 A, perpendicular out of the page
C. 40 A, perpendicular out of the page
D. 20 A, perpendicular into the page

Answer

D

Explanation

`B=(mu_(0)I)/(2pid)implies10^(-4)=(4pixx10^(-7)xxI)/(4pi 2/100)` (No field due to wires passing (extension) through O)
`I=20A`