Question

A metal wire PQ of mass 10g lies at rest on two horizontal metal rails separated by 4.90cm (figure 34-E9). A vertically downward magnetic field of magnitude 0.800T exists in the space. The resistance of the circuit is slowly decreased and it is found that when the resistance goes below 20.0Ω, the wire PQ starts sliding on the rails. Find the coefficient of friction.

Answer 1

μR = F

=> μ × m × g = ilB

=> μ × 10 × 10^–3 × 9.8 = 6/20 x 4.9 x 10^-2 x 0.8

=> μ = (0.3 x 0.8 x 10^-2)/(2 x 10^-2) = 0.12