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Chapter 7 Practice Paper: D.C. Circuits — question paper

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Secondary 4 · Physics (G2 / G3)

Chapter 7 Practice Paper

D.C. Circuits

Duration: 40 minutes
Total: 30 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
  • Circuit descriptions may be used in place of sketches.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is 30.

Original practice material written for the MOE Physics syllabus. It is not an official MOE or school examination paper. Circuit symbols, series and parallel circuit rules, effective resistance, whole-circuit problems, potential dividers and potentiometers, thermistors and light-dependent resistors as input transducers.

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

  1. 1

    Three resistors of 4.0 Ω, 6.0 Ω and 10 Ω are connected in series. Their combined resistance is

    1. A1.7 Ω
    2. B6.7 Ω
    3. C20 Ω
    4. D240 Ω
    ( )
  2. 2

    In a parallel branch, which quantity is the same for every branch?

    1. Apotential difference
    2. Bcurrent
    3. Cresistance
    4. Dcharge per branch
    ( )
  3. 3

    A 6.0 Ω and a 3.0 Ω resistor are connected in parallel. The combined resistance is

    1. A2.0 Ω
    2. B9.0 Ω
    3. C4.5 Ω
    4. D0.50 Ω
    ( )
  4. 4

    The resistance of a light-dependent resistor in bright light compared with darkness is

    1. Amuch higher in light
    2. Bmuch lower in light
    3. Cexactly the same
    4. Dzero in both
    ( )
  5. 5

    In a potential divider made of a 4.0 kΩ and an 8.0 kΩ resistor across a 12 V supply, the output taken across the 8.0 kΩ resistor is

    1. A4.0 V
    2. B6.0 V
    3. C8.0 V
    4. D12 V
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 1

    A 12 V battery of negligible internal resistance is connected to a 4.0 Ω resistor in series with a parallel pair made of a 6.0 Ω and a 3.0 Ω resistor.

    1. (a)

      Calculate the effective resistance of the parallel pair.

      resistance =Ω[2]
    2. (b)

      Calculate the current supplied by the battery.

      current =A[2]
    3. (c)

      Calculate the potential difference across the parallel pair.

      p.d. =V[2]
    4. (d)

      Calculate the current in the 3.0 Ω resistor.

      current =A[2]
  2. 2

    Two identical lamps, each rated 6.0 V 3.0 W, are connected (i) in series and then (ii) in parallel across a 6.0 V battery of negligible internal resistance. (Use each lamp’s resistance from its rating.)

    1. (a)

      Calculate the resistance of one lamp from its rating.

      resistance =Ω[2]
    2. (b)

      Calculate the battery current when the lamps are in series.

      current =A[2]
    3. (c)

      Calculate the battery current when the lamps are in parallel.

      current =A[2]
  3. 3

    A sensor circuit uses a 10 V supply feeding a potential divider made of a fixed 5.0 kΩ resistor and a thermistor. The output is taken across the thermistor.

    1. (a)

      At room temperature the thermistor’s resistance is 15 kΩ. Calculate the output voltage.

      output =V[2]
    2. (b)

      The thermistor warms and its resistance falls to 5.0 kΩ. Calculate the new output.

      output =V[2]
    3. (c)

      Explain how this circuit can act as an over-temperature alarm: state what happens to the output as the thermistor warms, and how a warning light should therefore be triggered.

      [2]

— End of paper —