A LevelPhysicsAQAExam Questions5. Electricity5.4 Electromotive Force & Internal Resistance

Electromotive Force & Internal Resistance (AQA A Level Physics)

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5.4 Electromotive Force & Internal Resistance

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5.4 Electromotive Force & Internal Resistance

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11 mark

What are the units of an electromotive force?

  • Newton, N

  • Ampere, A

  • Volt, V

  • Coulomb, C

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21 mark

What is the current in a cell of emf 5 V and internal resistance 5 Ω, when connected to a lamp of resistance 200 Ω?

  • 0.10 A

  • 0.050 A

  • 0.025 A

  • 0.024 A

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31 mark

Which of the following statements about internal resistance is correct?

  • The internal resistance of a cell is measured in amperes

  • When the internal resistance is zero, the terminal pd of a cell is equal to its emf

  • Internal resistance of a cell is due to resistance in the circuit wires  

  • Internal resistance within a cell increases its emf 

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41 mark

Which of the following graphs shows the correct variation of terminal potential difference V of a cell with current I?

q4_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

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    51 mark

    A graph showing the variation of terminal potential difference V of a cell with the current I flowing through it is shown:

    q5_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

    What is represented by the magnitude of the gradient of the graph?

    • The internal resistance of the cell

    • The terminal potential difference provided by the cell

    • The current through the cell  

    • The external resistance in the circuit

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    61 mark

    When current flows in a cell, which of the following statements correctly compares the terminal potential difference V provided by the cell to its emf, ε?

    • V = ε 

    • Vless thanε

    • εless thanV

    • V = ε2

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    71 mark

    A graph is drawn which shows the variation of terminal potential difference V of a cell with the current through it is I.

    q7_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

    Which row of the table, A to D, gives the magnitude of the emf ε and internal resistance r of the cell?

     

    emf ε  / V

    internal resistance r / Ω
    A 3 6.0
    B 3 0.5
    C 6 0.5
    D 6 3.0

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      81 mark

      Which of the following statements about the emf ε  of a cell is correct?

      • The emf is measured in Newtons

      • ε  = IR + Ir2 where R is the load resistance and r is the internal resistance

      • ε  is the amount of chemical energy transferred to electric energy, per unit of charge through a cell

      • The emf of a cell is always less than its terminal – or output – potential difference

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      91 mark

      A student measures the emf of a cell by connecting a voltmeter directly across the terminals.

      They record a measurement of 6.0 V.

      If the internal resistance of the cell is 0.5 Ω, what is the terminal potential difference measured by the voltmeter when a current of 200 mA flows through the cell?

      • 7.0 V

      • 6.0 V

      • 5.9 V

      • 5.8 V

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      101 mark

      Which of the following rows, A to D, is not a possible set of values for the emf ε and terminal potential difference V of a cell?  

       

      ε / V

      V / V
      A 5.0 6.0
      B 5.0 4.0
      C 6.0 6.0
      D 4.0 3.0

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        11 mark

        A battery of e.m.f. 12 V and internal resistance 2.0 Ω is connected in series with an ammeter of negligible resistance and an external resistor. External resistors of various different values are used.q11_electromotive-force--internal-resistance_aqa-as-physics-mcq

        Which combination of current and resistor value is not correct?

         

        current / A

        external resistor value / Ω
        A 1.0 10.0
        B 1.2 8.0
        C 1.5 6.0
        D 1.8 4.0

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          21 mark

          A simple circuit is formed by connecting a resistor of resistance R between the terminals of a battery of electromotive force (e.m.f.) 9.0 V and constant internal resistance r.q2_electromotive-force--internal-resistance_medium_aqa-as-physics-mcq

          A charge of 6.0 C flows through the resistor in a time of 2.0 minutes, causing it to dissipate 48 J of thermal energy. 

          What is the internal resistance r of the battery?

          • 0.17 Ω

          • 0.33 Ω

          • 20 Ω

          • 160 Ω

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          31 mark

          A student found two unmarked resistors. To determine the resistance of the resistors, the circuit below was set up. The resistors were connected in turn between P and Q, noting the current readings.

          The voltage readings were noted without the resistors and with each resistor in turn.q3_electromotive-force--internal-resistance_medium_aqa-as-physics-mcq

          The results were entered into a spreadsheet, as shown.

          1.5

          1.3

          28

          46

          1.5

          1.4

          14

          100

          The student forgot to enter the column headings.

          Which order of the headings would be correct?

          • e.m.f / V

            V / V

            R / Ω

            I / mA

          • V / V

            e.m.f / V

            R / Ω

            I / mA

          • V / V

            e.m.f / V

            I / mA

            R / Ω

          • e.m.f / V

            V / V

            I / mA

            R / Ω

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          41 mark

          A battery, with a constant internal resistance, is connected to a resistor of resistance 250 Ω, as shown.q4_electromotive-force--internal-resistance_medium_aqa-as-physics-mcq

          The current in the resistor is 40 mA for a time of 60 s. During this time 6.0 J of energy is lost in the internal resistance.

          What is the energy supplied to the external resistor during the 60 s and the e.m.f. of the battery?

           

          energy / J

          e.m.f / V
          A 2.4 2.4
          B 2.4 7.5
          C 24 10.0
          D 24 12.5

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            51 mark

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

            q5_electromotive-force--internal-resistance_medium_aqa-as-physics-mcq

            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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            61 mark

            Three cells each have an e.m.f. ε = 1.2 V and an internal resistance r = 0.8 Ω.

            Which combination of these cells will deliver a total e.m.f. of 1.2 V and a maximum current of 4.5 A?

            q6_electromotive-force--internal-resistance_medium_aqa-as-physics-mcq

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              71 mark

              A battery is connected to a 20 Ω resistor and a switch in series. A voltmeter is connected across the battery.

              When the switch is open the voltmeter reads 3.82 V. When the switch is closed the reading is 3.35 V.

              What is the internal resistance of the battery?

              • 1.3 Ω

              • 1.4 Ω

              • 2.5 Ω

              • 2.8 Ω

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              81 mark

              A cell of emf ε and internal resistance r is connected to an external load of resistance R as shown.

              q18_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

              Which of the following statements is incorrect?

              • begin mathsize 16px style V subscript 1 end style = begin mathsize 16px style V subscript 2 end style

              • ε  begin mathsize 16px style greater than end stylebegin mathsize 16px style V subscript 1 end style

              • begin mathsize 16px style V subscript 2 space greater than space end styleε 

              • ε  begin mathsize 16px style greater than end stylebegin mathsize 16px style V subscript 2 end style

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              9
              Sme Calculator              1 mark

              A circuit is set up such that a cell of emf E and internal resistance r is connected to a variable resistor R. 

              q19_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

              The load resistance R is varied such that a graph of the quantity IR can be plotted against the current I, using readings from the ammeter.

              q19_2_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

              Which row, A to D, gives the correct values for the emf E of the cell, its internal resistance r and the power dissipated in the load resistance when the current is 1.5 A, begin mathsize 16px style P subscript 1.5 end subscript end style ?

               

              ε / V

              I / A

              begin mathsize 14px style bold italic P subscript bold 1 bold. bold 5 end subscript end style / W
              A 6.0 0.7 3.7
              B 4.0 1.5 3.7
              C 6.0 1.5 5.6
              D 6.0 0.7 5.6

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                101 mark

                A cell of emf E and internal resistance r is connected to a load resistor R as shown:

                q20_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

                Pairs of values for the reading on the voltmeter V and R is given:

                V / V

                R / Ω

                3.0

                2.0

                4.0

                4.0

                What is the internal resistance of the cell?

                • 0.5 Ω 

                • 1.0 Ω    

                • 2.0 Ω 

                • 3.0 Ω 

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                11 mark

                A battery of electromotive force ε delivers charge Q to the load resistance.

                Which of the following statements is correct?

                • The work done in the external circuit is εQ 

                • The work done in the battery is εQ

                • The load resistance is εQ

                • The total energy dissipation in the battery and the load resistance is εQ 

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                21 mark

                Two cells, X and Y, of emf and internal resistance begin mathsize 16px style epsilon subscript X end style,  begin mathsize 16px style r subscript X end style and begin mathsize 16px style ϵ subscript Y end style, begin mathsize 16px style r subscript Y end style respectively, are connected in turn to a variable resistor R.

                The emf of cell Y is 50% the emf of cell X.

                Which expression gives the terminal potential difference V that equalises the current in both circuits?

                • begin mathsize 16px style ϵ subscript y end style begin mathsize 16px style open parentheses fraction numerator r subscript X minus 2 r subscript Y over denominator r subscript X minus r subscript Y end fraction close parentheses end style

                • begin mathsize 16px style ϵ subscript X end style begin mathsize 16px style open parentheses fraction numerator r subscript X minus 2 r subscript Y over denominator r subscript X minus r subscript Y end fraction close parentheses end style

                • begin mathsize 16px style ϵ subscript y end style begin mathsize 16px style open parentheses fraction numerator r subscript X minus space r subscript Y over denominator r subscript X minus space 2 r subscript Y end fraction close parentheses end style

                • begin mathsize 16px style ϵ subscript y end style begin mathsize 16px style open parentheses fraction numerator r subscript X minus 2 r subscript Y over denominator 2 r subscript X minus r subscript Y end fraction close parentheses end style

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                31 mark

                A cell of emf E and internal resistance r is connected to a variable resistor R.

                q23_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

                Which of the following statements about the circuit is / are correct?

                1. If the resistance of R decreases, the terminal potential difference also decreases but the power dissipated in the cell is large
                2. If the resistance of R is very large, the current in the circuit is very small but most of the power supplied by the cell is dissipated by R
                3. If the resistance of R is very large, the power dissipated in R tends towards the value begin mathsize 16px style E squared over R end style

                • Statement 1 only

                • Statement 2 only

                • Statement 1 and 3 only

                • Statement 1, 2 and 3

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                41 mark

                A 10 V supply with an unknown internal resistance r is connected to two 25 kΩ resistors as shown.

                q24_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

                A non-ideal voltmeter, of resistance 100 kΩ, is connected in parallel with one of the resistors.

                What is the internal resistance of the supply if the voltmeter reads 4.0 V?

                • 1 kΩ  

                • 3 kΩ 

                • 5 kΩ 

                • 7 kΩ 

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                51 mark

                A cell of emf E and internal resistance r is connected to a variable load resistance, R. 

                Which of the following graphs correctly shows how the power dissipated across the load resistance begin mathsize 16px style P subscript R end style varies with load resistance R?

                q25_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

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                  61 mark

                  Two lamps, L1 and L2, of resistance 11 Ω and 22 Ω respectively, are connected in turn in series and in parallel to a cell with emf 40 V and internal resistance 7 Ω.

                  q26_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

                  Which lamp(s) shine(s) the brightest?  

                  • L1 when connected in parallel

                  • L1 when connected in series 

                  • L2 when connected in series 

                  • L1 and L2 when connected in parallel 

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                  71 mark

                  A circuit is designed to measure the emf of a cell E which has an internal resistance of 0.75 Ω (you may assume the 2.0 V cell is of negligible resistance). 

                  q27_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

                  There is zero current in E when the variable resistor is set at 3.0 Ω.

                  What is the emf of cell E?

                  • 1.0 V

                  • 1.3 V

                  • 2.0 V 

                  • 3.0 V 

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                  81 mark

                  A uniform wire of length 110 cm and radius 0.55 mm is attached between X and Y in series with a cell of emf 3.0 V and internal resistance 0.80 Ω.

                  q28_electromotive-force-_-internal-resistance_aqa-as-physics-mcq

                  The wire has a resistivity of 1.1 × 10–6 Ω m–1.

                  A cell C of emf 1.5 V and internal resistance 0.50 Ω is also connected to the circuit, with a moveable contact J which can be connected to any point along XY.  

                  How far from X is the moveable contact J when there is no current through the cell C?

                  • 0.89 m

                  • 0.70 m

                  • 0.54 m 

                  • 0.50 m 

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                  91 mark

                  Which of the following rows, A to D, is not a possible set of values for the emf ε and internal resistance r of a cell with the current I through it?  

                   

                  ϵ / V

                  I / A

                  r / Ω
                  A 5.0 4.0 1.25
                  B 5.0 0.0 200
                  C 6.0 6.0 2.00
                  D 4.0 0.020 200

                     

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                    101 mark

                    Which of the following statements most accurately explains the electromotive force of a cell?

                    • The difference in energy between that needed to drive unit charge through the load resistors and through the cell

                    • The work done to drive a unit charge through the internal resistance of the cell

                    • The work done to drive a unit charge through the load resistance in the circuit

                    • The total work done to drive a unit charge round a complete circuit 

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