Practice question

**Series combination** R_eq = R₁+R₂+..., same current I through each, voltage divides proportionally V_i = I R_i. Parallel combination 1/R_p = 1/R₁+1/R₂+..., same voltage V across each, current divides inversely, equivalent R_p = (R₁ R₂)/(R₁+R₂) for two resistors. Equivalent emf: εₑq = 3 + 5 = 8 V . Total resistance: Rtₒtₐl = r₁ + r₂ + R = 1 + 3 + 4 = 8 Ω . Current: I = (εₑq/Rtₒtₐl) = (8/8) = 1 A . Applying I = n e A v_d, R = ρ l/A, R_t = R₀[1+αΔT], Kirchhoff's ΣI=0, ΣV=0, R_eq series/parallel, V = ε - I r and P