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

Answer

A

Explanation

Suppose in equilibrium wire `PQ` lies at a distance `r` above the wire `AB`
Hence in equilibrium `mg=Bilimpliesmg=(mu_(0))/(4pi)((2i)/(r )) xxil`
` implies10^(-3)xx10=10^(-7)xx(2xx(50^(2)))/(r )=0.5impliesr=25mm`