Two long straight cylindrical conductors with resistivities ρ₁ and ρ₂ respectively are joined together as shown in the figure. If current I flows through the conductors, the magnitude of the total free charge at the interface of the two conductors is:

Question

G1 Physics · Accepted Answer

At the interface, E₁ = ρ₁J and E₂ = ρ₂J. The surface charge density is σ = ε₀(E₂-E₁), and with J = I/A the total interface charge is ε₀I(ρ₂-ρ₁) in magnitude. Hence option C.