An infinetely long conductor PQR is bent tor form a right angle as shown in Fig. A current I flows through PQR. The magnetic field due to this current carrying conductor at the point M is `B_1`. Now, another infinitely long straight conductor QS, is connected at Q so that the current is `1/2I` in QR as well as in QS, is the current in PQ remaininig unchanged. The magnetic field at M is now `B_2`. The ratio `B_1//B_2` is given by

Options

A. `1//2`
B. `1`
C. `2//3`
D. `2`

Answer

C

Explanation

(c) `vecB_1=(mu_0I)/(4piR)odot, vecB_2=(mu_0I)/(4piR)+(mu_0I//2)/(4piR)odot`
`implies B_2=(mu_0I)/(4piR)(3/2)odot implies |(B_1)/(B_2)|=2/3`