Question

Determine the voltage Vab for the first circuit and also determine the voltages Vab and Vcd for the second circuit

Answer 1

Vab= E = 20V

because I = 0 and the voltage drop across the resistances R1 and R2 is also 0.

Second circuit:

Vab = 10V (no voltage drop across R1)

Vcd= E2-E1 = 20V

Series connection of voltage sources. But the sources are connected to the contrary and voltage drop across R1 or R2 is 0 V.