In the circuit shown in Figure, AB is a uniform wire of length L = 5 m. It has a resistance of 2 Ω/m. When AC = 2.0 m, it was found that the galvanometer shows zero reading when switch S is placed in either of the two positions 1 or 2. Find the emf E₁.

Question

G1 Physics · Accepted Answer

Image Resistance of AC = 4 Ω and CB = 6 Ω. Zero galvanometer current for both switch positions means point C has the same potential as each selected top node. Applying the balance condition to the two source branches with E₃ = 30 V, E₂ and R = 10 Ω as shown gives E₁ = 20 V.