An infinitely long conductor PQR is bent to form a right angle as shown. A current I flows through PQR. The magnetic field due to this current at the point `M is B_(1)`. Now, another infinitely long straight conductor QS is connected at Q so that the current is `I//2` in QR as well as in QS, the current in PQ remaining unchanged. The magnetic field at M is now `B_(2) = 4 mT`. Find the value of `B_(1) ("in" mT)`.

Answer

3

Explanation

`B_(1)=(mu_(0)I)/(4 pi R)`
`B_(2)=(mu_(0)I)/(4pi R) + (mu_(0)(I/2))/(4 pi R) = 3/4 (mu_(0)I)/(4 pi R)`
`(B_1)/(B_2) = 3/4 implies B_(2)= 3/4 B_(2) = 3/2 xx 4 = 3 mt`.