Syllabus Edition

First teaching 2023

First exams 2025

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Potential Dividers (CIE A Level Physics)

Exam Questions

2 hours37 questions
1
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1 mark

A potential divider consists of a fixed resistor R and a light-dependent resistor (LDR)

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What happens to the voltmeter reading, and why does it happen, when the intensity of light on the LDR increases?

  • The voltmeter reading decreases because the LDR resistance decreases

  • The voltmeter reading decreases because the LDR resistance increases

  • The voltmeter reading increases because the LDR resistance decreases

  • the voltmeter reading increases because the LDR resistance increases

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2
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1 mark

The diagram shows a potentiometer circuit.

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The contact T is placed on the wire and moved along the wire until the galvanometer reading is zero. The length XT is then noted.

 In order to calculate the potential difference per unit length of the wire XY, which value must also be known?

  • the e .m .f. of the cell E1

  • the e. m .f. of the cell E2

  • the resistance of resistor R

  • the resistance of the wire XY

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3
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1 mark

A source of e.m.f. 9.0 mV has an internal resistance of 6.0 Ω.

It is connected across a galvanometer of resistance 30 Ω.

What is the current in the galvanometer?

  • 250 µA

  • 300 µA

  • 1.5 mA

  • 2.5 mA

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4
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1 mark

The unknown e.m.f. E of a cell is to be determined using a potentiometer circuit. The balance length is to be measured when the galvanometer records a null reading.

 What is the correct circuit to use ?

cie-ial-images576png

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    5
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    1 mark

    The diagram shows a potential divider circuit designed to provide a variable output p. d.

    cie-ial-images578png

    Which gives the available range of output p. d ?

     

     

    Maximum output

    Minimum output

    A

    B

    C

    D

    3.0 V

    4.5 V

    9.0 V

    9.0 V

    0

    0

    0

    4.5 V

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      6
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      1 mark

      Which diagram shows a potential divider circuit that can vary the voltage across the lamp ?

      cie-ial-images579png

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        7
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        1 mark

        In the circuit shown, the 6.0 V battery has negligible internal resistance. Resistors R1 and R2 and the voltmeter have resistance 100 kΩ.

        cie-ial-images580png

        What is the current in the resistor R2?

        • 20 µA

        • 30 µA

        • 40 µA

        • 60 µA

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        8
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        1 mark

        Which electrical component is represented by the following symbol ?

        cie-ial-images581png

        • a diode

        • a potentiometer

        • a galvanometer

        • a thermistor

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        9
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        1 mark

        The circuit is designed to trigger an alarm system when the input voltage exceeds some preset value. It does this by comparing V out with a fixed reference voltage, which is set at 4.8 V .

        cie-ial-images585png

        V out is equal to 4.8 V. 

         What is the input voltage Vin?

        • 4.8 V

        • 7.2 V

        • 9.6 V

        • 12 V

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        10
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        1 mark

        A low-voltage supply with an e. m. f. of 20 V and an internal resistance of 1.5 Ω is used to supply power to a heater of resistance 6.5 Ω in a fish tank.

         What is the power supplied to the water in the fish tank ?

        • 41 W

        • 50 W

        • 53 W

        • 62 W

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        1
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        1 mark

        The diagram shows a potential divider circuit which, by adjustment of the contact X, can be used to provide a variable potential difference between the terminals P and Q.

        cie-ial-images586png

        What are the limits of this potential difference?

        • 0 and 5 V

        • 0 and 20 V

        • 0 and 25 V

        • 5 V and 25 V

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        2
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        1 mark

        In the circuit below, P is a potentiometer of total resistance 10 Ω and Q is a fixed resistor of resistance 10 Ω. The battery has an e .m f. of 4.0 V and negligible internal resistance. The voltmeter has a very high resistance .

        cie-ial-images587png

        The slider on the potentiometer is moved from X to Y, and a graph of voltmeter reading V is plotted against slider position.

         Which graph would be obtained ?

        cie-ial-images588png

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          3
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          1 mark

          In the circuit below, the ammeter reading is I, and the voltmeter reading is V.

          cie-ial-images590png

          When the switch is closed, which row describes what happens to I and V?

           

           

          I

          V

          A

          B

          C

          D

          decreases

          increases

          increases

          stays the same

          decreases to zero

          stays the same

          decreases to zero

          increases

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            4
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            1 mark

            The diagram shows a potential divider connected to a 9.0 V supply of negligible internal resistance.

            cie-ial-images591png

            What range of voltages can be obtained between P and Q?

            • zero to 1.5 V

            • zero to 7.5 V

            • 1.5 V to 7.5 V

            • 1.5 V to 9.0 V

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            5
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            1 mark

            A potential divider consisting of resistors of resistance R1 and R2 is connected to an input potential difference of V0 and gives an output p .d. of V.

            cie-ial-images592png

            What is the value of V ?

            • fraction numerator V subscript 0 space R subscript 1 over denominator R subscript 2 end fraction

            • fraction numerator V subscript 0 space R subscript 1 over denominator R subscript 1 plus R subscript 2 end fraction

            • fraction numerator V subscript 0 space R subscript 2 over denominator R subscript 1 plus R subscript 2 end fraction

            • fraction numerator V subscript 0 open parentheses R subscript 1 plus R subscript 2 close parentheses over denominator R subscript 1 end fraction

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            6
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            1 mark

            A potential divider consists of resistors of resistance R1 and R2 connected in series across a source of potential difference V0. The potential difference across R1 is V out .

            cie-ial-images593png

            Which changes to R1 and R2 will increase the value of V out ?

             

             

            R1

            R2

            A

            B

            C

            D

            doubled

            doubled

            halved

            halved

            doubled

            halved

            doubled

            halved

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              7
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              1 mark

              A 12 V battery is in series with an ammeter, a 2 W fixed resistor and a 0 – 10 W variable resistor. High-resistance voltmeters P and Q are connected across the variable resistor and the fixed resistor, respectively, as shown.

              cie-ial-images594png

              The resistance of the variable resistor is changed from its maximum value to zero.

              Which graph shows the variation with current of the voltmeter readings?

              cie-ial-images595png

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                8
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                1 mark

                A potentiometer is used as shown to compare the e. m. f. s of two cells.

                cie-ial-images596png

                The balance points for cells X and Y are 0.70 m and 0.90 m respectively.

                 If the e. m .f. of cell X is 1.1 V, what is the e .m. f. of cell Y ?

                • 0.69 V

                • 0.86 V

                • 0.99 V

                • 1.4 V

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                9
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                1 mark

                A potential divider circuit consists of fixed resistors of resistance 2.0 Ω and 4.0 Ω connected in series with a 3.0 Ω resistor fitted with a sliding contact. These are connected across a battery of e. m .f. 9.0 V and zero internal resistance, as shown.

                cie-ial-images597png

                What are the maximum and the minimum output voltages of this potential divider circuit?

                 

                 

                Maximum voltage / V

                Minimum  voltage / V

                A

                B

                C

                D

                4.0

                5.0

                9.0

                9.0

                2.0

                2.0

                0

                2.0

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                  10
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                  1 mark

                  A battery with e.m.f. E and internal resistance r is connected in series with an external variable resistor.

                  cie-ial-images5978png

                  The value of the external resistance R is slowly increased from zero.

                   Which statement is correct ? (Ignore any temperature effects.)

                  • the potential difference across the external resistance decreases

                  • the potential difference across the internal resistance increases

                  • the power dissipated in r increases and then decreases

                  • the power dissipated in R increases and then decreases

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                  1
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                  1 mark

                  In the potentiometer circuit shown, the reading on the ammeter is zero.

                  cie-ial-images5979png

                  The light-dependent resistor (LDR) is then covered up, and the ammeter gives a non-zero reading.

                   Which change could return the ammeter reading to zero?

                  • decrease the supply voltage

                  • increase the supply voltage

                  • move the sliding contact to the left

                  • move the sliding contact to the right

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                  2
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                  1 mark

                  A power supply and a solar cell are compared using the potentiometer circuit shown.

                  cie-ial-images599png

                  The e.m.f. produced by the solar cell is measured on the potentiometer.

                   The potentiometer wire PQ is 100.0 cm long and has a resistance of 5.00 Ω. The power supply has an e. m .f. of 2.000 V, and the solar cell has an e .m. f. of 5.00 mV.

                  Which resistance R must be used so that the galvanometer reads zero when PS = 40.0 cm ?

                  • 395 Ω

                  • 795 Ω

                  • 995 Ω

                  • 1055 Ω

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                  3
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                  1 mark

                  The diagrams show the same cell, ammeter, potentiometer and fixed resistor connected in different ways.

                  cie-ial-images600png

                  The distance d between the sliding contact and a particular end of the potentiometer is varied. The current measured is then plotted against the distance d.

                   For which two circuits will the graphs be identical ?

                  • W and X

                  • W and Y

                  • X and Y

                  • Y and Z

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                  4
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                  1 mark

                  In the circuit shown, XY is a length L of uniform resistance wire. R1 and R2 are unknown resistors. J is a sliding contact that joins the junction of R1 and R2 to points on XY through a small signal lamp S.

                  cie-ial-images602png

                  To determine the ratio  V subscript 1 over V subscript 2  of the potential differences across R1 and R2, a point is found on XY at which the lamp is off. This point is at a distance x from X.

                   What is the value of the ratio V subscript 1 over V subscript 2   ?

                  • L over x

                  • x over L

                  • fraction numerator L minus x over denominator x end fraction

                  • fraction numerator x over denominator L minus x end fraction

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                  5
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                  1 mark

                  In the potentiometer circuit below, the moveable contact is placed at N on the bare wire XY, such that the galvanometer shows zero deflection.

                  cie-ial-images603png

                  The resistance of the variable resistor is now increased.

                   What is the effect of this increase on the potential difference across the wire XY and on the position of the moveable contact for zero deflection ?

                   

                   

                  Potential difference across XY

                  Position of moveable contact

                  A

                  B

                  C

                  D

                  increases

                  increases

                  decreases

                  decreases

                  nearer to X

                  nearer to Y

                  nearer to X

                  nearer to Y

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                    6
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                    1 mark

                    The graph below shows how resistance R of a thermistor varies during part of a day.

                     cie-ial-images604png

                    The thermistor is connected to the potential divider circuit as shown.

                    cie-ial-images605png

                    At 0730, an output of 6.0 V is required.

                     What value of the variable resistor should be set at this time?

                    • 1.5 kΩ

                    • 3.0 kΩ

                    • 4.5 kΩ

                    • 6.0 kΩ

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                    7
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                    1 mark

                    The contact is connected one at a time to points X, Y and Z to test the circuit. The lamps do not light up because lamp L is blown.

                    cie-ial-images606png

                    Which of the following are the readings of the voltmeter when the contact is connected to each of the points?

                     

                     

                    X

                    Y

                    Z

                    A

                    B

                    C

                    D

                    12 V

                    8 V

                    12 V

                    8 V

                    8 V

                    8 V

                    12 V

                    12 V

                    4 V

                    0 V

                    0 V

                    4 V

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                      8
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                      1 mark

                      A potential divider has a constant supply of 6.0 V, as shown in the diagrams.

                       Which circuit will provide a potential difference between X and Y that can be varied between zero and 3.0 V ?

                      cie-ial-images607png

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                        9
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                        1 mark

                        The resistance R of an unknown resistor is compared with a fixed 100 Ω resistor using the circuit as shown in the diagram.

                         The balance length l is 30.0 cm and 48.3 cm when P is connected to Q and R, respectively. 

                        cie-ial-images608png

                        The length of the wire XY is 100 cm and has a resistance of 40 Ω. The two cells E1 and E2, have negligible internal resistances.

                         What is the value of resistance R ?

                        • 38 Ω

                        • 47 Ω

                        • 61 Ω

                        • 161 Ω

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