A long wire `AB` is placed on a table. Another wire `PQ` of mass `1.0 g` and length `50cm` is set to slide on two rails `PS` and `QR`. A current of `50 A` is passed through the wires. At what distance above `AB`, will the wire `PQ` be in equilibrium?

Options

A. 25 mm
B. 50 mm
C. 75 mm
D. 100 mm

Answer

A

Explanation

At equilibrium - mg = Bil
`implies mg = (mu_(0))/(4pi) ((2i)/( r)) xx il`
`implies 10^(-3) xx 10 = 10^(-7) xx (2 xx (50)^(2))/(r ) xx 0.5`
`implies r = 25` mm