As the two cells oppose each other hence, the effective emf in closed circuit is 15−10=5V and net resistance is 1+0.6=1.6Ω (because in the closed circuit the internal resistance of two cells are in series. Current in the circuit, I=
effective emf
total resistance
=
5
1.6
A The potential difference across voltmeter will be same as the terminal voltage of either cell. Since the current is drawn from the cell of 15V ∴V1=E1−Ir1 =15−