Two vertical conducting rails 1 m apart are connected by R₁ and R₂. A horizontal bar of mass 0.2 kg slides down without friction in B=0.6 T perpendicular to the rail plane. At terminal speed, powers in R₁ and R₂ are 0.76 W and 1.2 W. Find terminal speed, R₁ and R₂.

Question

G1 Physics · Accepted Answer

At terminal speed, magnetic force balances weight: mg=Bℓ(I₁+I₂). The powers are P₁=I₁²R₁=0.76 W and P₂=I₂²R₂=1.2 W. The same motional emf ε=Bℓv appears across both branches. Solving gives v=1 m/s, R₁=0.5 Ω and R₂=0.30 Ω. Hence option A.