Lesson 6.1.2

6.1.2 Energy Quiz: OCR Physics, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.1.2, Energy: 20 multiple choice questions for the OCR Physics (H156), Unit 5: Particles and medical physics, written with Revision Ninja.

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The 20 questions

  1. What physical quantity is represented by the area under a potential difference against charge graph for a capacitor?

    • Electric field strength
    • Energy stored
    • Electric potential
    • Capacitance

  2. Which expression gives the energy W stored by a capacitor of capacitance C charged to potential difference V?

    • C V^2
    • 0.5 C^2 V
    • 0.5 C V^2
    • C / V^2

  3. What is the SI unit for the time constant of a capacitor-resistor circuit?

    • Farad
    • Coulomb
    • Ohm
    • Second

  4. What device uses a rapid discharge of stored capacitor energy to restart a patient's heart?

    • Defibrillator
    • Voltmeter
    • Pacemaker
    • Transformer

  5. What is the time constant of a circuit containing a 10 microfarad capacitor and a 100 kilohm resistor?

    • 10 s
    • 1.0 s
    • 100 s
    • 0.1 s

  6. How much energy is stored in a 200 microfarad capacitor charged to a potential difference of 100 volts?

    • 0.01 J
    • 1.0 J
    • 2.0 J
    • 100 J

  7. After one time constant, what percentage of initial charge remains on a discharging capacitor?

    • 37%
    • 0%
    • 63%
    • 50%

  8. When charging a capacitor through a resistor, what percentage of maximum charge is reached after one time constant?

    • 63%
    • 100%
    • 50%
    • 37%

  9. What is the gradient of a graph of natural log of charge against time for a discharging capacitor?

    • 1 / CR
    • CR
    • -CR
    • -1 / CR

  10. What mathematical feature characterises the decay of charge on a discharging capacitor over equal time intervals?

    • Linear decrease
    • Increasing rate
    • Constant gradient
    • Constant ratio

  11. What happens to the time constant of a circuit if resistance is doubled and capacitance is halved?

    • Remains unchanged
    • Doubles
    • Halves
    • Quadruples

  12. In spreadsheet modelling of capacitor discharge, what expression represents the rate of change of charge Delta Q over Delta t?

    • -CR / Q
    • Q / CR
    • -Q / CR
    • -Q * CR

  13. A capacitor stores 0.02 coulombs of charge when the potential difference across it is 10 volts. What energy is stored?

    • 0.05 J
    • 2.00 J
    • 0.20 J
    • 0.10 J

  14. What fraction of the total energy supplied by a power supply is stored in a charging capacitor?

    • Three quarters
    • Half
    • Quarter
    • All

  15. Approximately how many time constants does it take for a capacitor to discharge to less than 1% of its initial charge?

    • 10
    • 5
    • 2
    • 1

  16. Which instrument can be connected across a capacitor to record fast potential difference changes directly to a computer?

    • Signal generator
    • Data-logger
    • Joulemeter
    • Coulombmeter

  17. What physical quantity does the gradient of a charge against time graph represent for a discharging capacitor?

    • Resistance
    • Current
    • Energy
    • Capacitance

  18. Two identical capacitors are connected in parallel and charged to voltage V. How does total stored energy compare to one capacitor?

    • Same
    • Double
    • Half
    • Four times

  19. Two identical capacitors are connected in series across potential difference V. How does total stored energy compare to one capacitor?

    • Half
    • Same
    • Quarter
    • Double

  20. Why are capacitors used instead of rechargeable batteries in camera flash units?

    • Longer charge retention
    • Rapid energy release
    • Lower cost
    • Higher energy density

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