Physics (AS & A Level) · Feb / March 2025 · Paper 12 · Question 36

A cell of electromotive force (e.m.f.) E and internal resistance r is connected in series with a switch S and an external resistor of resistance R. The potential difference (p.d.) between P and Q is V. Which statement is correct when S is changed from open to closed?

1. AV increases because there is a p.d. across R.
2. BV decreases because there is a p.d. across r.
3. CV remains the same because the decrease of p.d. across r is balanced by the increase of p.d. across R.
4. DV remains the same because the sum of the p.d.s across r and R is still equal to E.

As printed in the paper