O-LevelPhysicsElectricity5054/22 · Oct/Nov 2023 · Q77 Marks

An electric circuit contains a battery, a fixed resistor R, a voltmeter and a thermistor. Fig. 7.1 is an incomplete circuit diagram of the arrangement. [Figure 7.1] The thermistor is connected between terminals T₁ and T₂.

(a)Complete Fig. 7.1 by drawing the circuit symbol for a thermistor connected between T₁ and T₂.[1]
(b)(i)The resistance of R is 2.5Ω. The reading on the voltmeter is 0.40V. Calculate: the current in R current = .......................... A[2]
(b)(ii)the power transferred in R. power = .......................... W[2]
(c)The temperature of the thermistor increases. Explain what happens to the reading on the voltmeter.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.

[1] and drawn between T₁ and T₂
[1] (I =) V / R or 0.40 / 2.5
[1] 0.16 (A)
[1] (P =) VI or 0.40 × 0.16 or (P =) I²R or 0.16² × 2.5
[1] 0.064 (W)
[1] resistance (of the thermistor / circuit) decreases
[1] increase in current in circuit / R takes a larger proportion of the total resistance / voltage and voltmeter reading / it increases.

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.