Question:
A long straight wire carrying a current of 25 A rests on a table as shown in the figure. Another wire PQ of length 1 m, mass 2.5 g carries the same current but in the opposite direction. The wire PQ is free to slide up and down. To what height will PQ rise?
Solution:
The magnetic field produced by a long straight current-carrying wire is given as
B = μ0I/2πh
Magnetic force on the small conductor is F = BIl sin θ = BIl
F = mg = μ0I2l/2πh
h = 0.51 cm