O-LevelPhysicsElectricity5054/21 · Oct/Nov 2023 · Q67 Marks
Fig. 6.1 shows a circuit that contains two identical cells, each of e.m.f. 1.5 V, that are connected in parallel. The circuit also contains two ammeters, a thermistor T and two resistors R and S. [Figure 6.1] The reading on ammeter 1 is 0.20 A.
- (a)State why the reading on ammeter 2 is also 0.20 A.[1]
- (b)(i)Calculate the resistance of T. resistance = ........................................................................ Ω[3]
- (b)(ii)The temperature of T increases. Explain why the potential difference (p.d.) across T decreases.[3]
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Mark scheme
Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.
- [B1] (because) the current at every point in a series circuit is the same
- [C1] (R =) V / I or 1.5 / 0.20 or 7.5 (Ω)
- [C1] (RT =) 7.5 – 1.5 – 3.5
- [A1] 2.5 (Ω)
- [B1] resistance (of T / thermistor) decreases (as the temperature increases)
- [B1] current in circuit increases or smaller fraction of total resistance
- [B1] p.d. across R and S increases or (p.d. is) smaller fraction of e.m.f.
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