Exam-style Questions: Resistance

  1. Fig. 3.1 shows part of an electrical circuit.

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    Calculate the total resistance between A and B.

    resistance = ................. Ω

    (Marks available: 3)

  2. The heating element of an electric kettle operates at 230 V and has a power rating of 2.52 kW.

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    a) Calculate the working resistance R of the heating element.

    working resistance = ............... Ω

    (2 Marks)

    b) A digital multimeter is used to measure the resistance of the heating element when it is cold. The value of the resistance measured by this method is considerably lower than the working resistance.

    Suggest a reason for this.

    (1 Mark)

    (Marks available: 3)

  3. Calculate the total resistance between the points X and Y for the circuit shown in Fig. 3.1

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    resistance = .................... Ω

    (Marks available: 3)

Answer

Answer outline and marking scheme for question:

  1. Sum of the currents = zero (at junction)OR

    sum of the currents in = sum of currents out (at junction)

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    (3 Marks)

    (Marks available: 3)

  2. a) R = V2 / P / I = 10.96 A (1 Mark) m ; = 21.0 Ω (1 Mark) e

    (2 Marks)

    b) reference to element being colder and so lower resistance AW ora (NOT it is colder)

    (1 Mark)

    (Marks available: 3)

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    (3 Marks)

    (Marks available: 3)