A-LevelPhysicsD.C. circuits9702/12 · Feb/Mar 2025 · Q361 Mark

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. [Figure 36.1] The potential difference (p.d.) between P and Q is V. Which statement is correct when S is changed from open to closed?

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AV increases because there is a p.d. across R.

BV decreases because there is a p.d. across r.

CV remains the same because the decrease of p.d. across r is balanced by the increase of p.d. across R.

DV remains the same because the sum of the p.d.s across r and R is still equal to E.

✓ Correct answer

B: V decreases because there is a p.d. across r.

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Topic: D.C. circuits, A-Level Physics (syllabus 9702). Multiple choice, 1 mark.
Source: A-Level Physics, Feb/Mar 2025 Paper 1 Variant 2, question 36.

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