Two metal wires of identical dimension are connected in series. If σ₁ and σ₂ are the conductivities of the metal wires respectively, the effective conductivity of the combination is:
σ₁σ₂/(σ₁+σ₂)
(σ₁+σ₂)/(2σ₁σ₂)
(σ₁+σ₂)/σ₁σ₂
2σ₁σ₂/(σ₁+σ₂)
Solution:
here, Reff = R₁ + R₂ or (L + L) / σeffA = L / σ₁A + L / σ₂A (both wires are identical so have same cross section A) or 2 / σeff = 1 / σ₁ + 1 / σ₂ or σeff = 2σ₁σ₂ / (σ₁ + σ₂)