Question 6

6(a)1 mark

State Kirchhoff's first law.

State A short answer. No explanation is needed, and adding one cannot earn extra marks.

Your answer

Suggested time: 2 min

6(b)2 marks

A cell with internal resistance r is connected to two resistors of resistances R₁ and R₂ as shown in Fig. 6.1.

The potential differences (p.d.s) across R₁ and R₂ are V₁ and V₂ respectively. The terminal p.d. across the cell is V. The current in the circuit is I.

Use Kirchhoff's laws to show that the total resistance R_T of the external circuit is given by R_T = R₁ + R₂.

Fig. 6.1 — see the question text for what it shows

Using You must use the thing it names. An answer that reaches the right value another way may not score.

Your answer

Suggested time: 3 min

6(c)3 marks

A cell with internal resistance r is connected in series with two resistors R₁ and R₂ (Fig. 6.1). The electromotive force (e.m.f.) of the cell is 1.50 V. The values of R₁ and R₂ are 10 Ω and 15 Ω respectively. The terminal p.d. of the cell is 1.35 V.

Calculate the internal resistance r of the cell.

Calculate Show your working. The method can earn marks even when the final value is wrong, and a bare answer often cannot.

Your answer

Suggested time: 5 min

9702/21/M/J/24Cambridge International AS & A Level Physics 9702 · May/June 2024 · Paper 2 variant 1 · sit the whole paper