O-LevelPhysicsElectricity5054/21 · May/June 2023 · Q36 Marks

Fig. 3.1 shows a circuit containing three resistors, a 12V power supply and an ammeter. [Figure 3.1]

(a)Calculate the current in the 400 Ω resistor.[2]
(b)Calculate the power produced in the 400 Ω resistor.[2]
(c)A student uses all of the components shown in Fig. 3.1 in another circuit. She connects them so that there is the largest possible current in each resistor. The current in one of the resistors is larger than the current in the other two resistors. The student connects the ammeter into the circuit to measure the current in this resistor. Draw the circuit diagram of the arrangement. Label each resistor with the value of its resistance.[2]

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Mark scheme

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

[B1] (I =) V/R in any form or (total resistance =) 700 (Ω)
[B1] 0.017 (A)
[C1] (P =) I² R or VI and either V²/R or V=IR numerical or algebraic in any form or voltage across 400 Ω resistor = (a) × 400 (6.857 V)
[A1] 0.12 (W)
[B1] circuit drawn with all 3 resistors in parallel with cell / power supply
[B1] ammeter in series with 100 Ω resistor or in series with resistor with largest current in arrangement drawn

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