O-LevelPhysicsElectricity5054/21 · Oct/Nov 2025 · Q610 Marks

A circuit consists of a battery of e.m.f. 9.0V, a switch, a resistor P, an ammeter, a 4.0Ω resistor and a voltmeter. Fig. 6.1 is the circuit diagram of the circuit. [Figure 6.1]

(a)State Ohm's law.[2]
(b)(i)The switch in the circuit in Fig. 6.1 is closed. Calculate the reading on the ammeter.[2]
(b)(ii)Calculate the power transferred electrically to resistor P.[2]
(c)(i)Calculate the resistance of the reshaped resistor.[2]
(c)(ii)The reshaped resistor is connected into the circuit instead of resistor P. Calculate the new reading on the voltmeter. Show your working.[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

[B1] potential difference/p.d. (across a component) is directly proportional to the current (in the component)
[B1] at constant temperature/physical conditions
[C1] (ammeter reading =) V/R or E / (Rp + RQ) or 9.0 / (8.0 + 4.0)
[A1] 0.75 (A)
[C1] (power transferred =) IV or 0.75 × (0.75 × 8.0) or 0.75 × 6.0
[A1] 4.5 (W)
[C1] (length halves and so cross-sectional) area doubles or (new resistance =) 8.0 × 0.50 / 2.0
[A1] 2.0 (Ω)
[B1] (voltmeter reading =) ExRQ / (Rnew + RQ) or 9.0 x 4.0 / (2.0 + 4.0) or (I = ) 1.5 A
[B1] 6.0 (V)

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