A cell with electromotive force (e.m.f.) $E$ and internal resistance $r$ is connected in series to a switch $S$ and an external resistor of resistance $R$. The potential difference (p.d.) across P and Q is $V$. Which statement is correct when $S$ is moved from open to closed?
- A$V$ increases because there is a p.d. across $R$.
- B$V$ decreases because there is a p.d. across $r$.
- C$V$ remains the same because the decrease of p.d. across $r$ is balanced by the increase of p.d. across $R$.
- D$V$ remains the same because the sum of the p.d.s across $r$ and $R$ is still equal to $E$.