Numbers
CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Topic overviewResistance and Ohm's lawOhmic and non-ohmic behaviourResistors in series and in parallelInvestigating current, voltage and resistance in series and parallel circuitsElectrical power and energy in resistive circuitsResistivity and the equation R = ρl/AMeasuring the resistivity of a metalCurrent–voltage characteristics of a conductor, a lamp and a diodeResistance, temperature and superconductivity
Internal Resistance and Potential Dividers
Topic overviewInternal resistance and terminal potential differenceConsequences of internal resistance for external circuitsMeasuring electromotive force and internal resistanceThe potential divider and variable outputPotential dividers in lighting and heating control circuitsLoaded potential dividers and output voltage calculations
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Topic overviewSuperposition of wavesStanding waves, nodes and antinodesStanding waves on stretched stringsStanding waves in a pipe closed at one endMeasuring the speed of sound with a resonance tubeConditions for observable interferencePath difference and phase differenceYoung's double slitDiffraction at a single slitThe diffraction grating
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Topic overviewChoosing and using measuring instrumentsPrecision, accuracy and recording measurementsUsing the cathode ray oscilloscope to measure voltage and frequencyTables, graphs and presenting resultsLinearising a relationship and using the gradientAbsolute and percentage uncertaintyCombining uncertainties and uncertainty on a graphRandom and systematic error, reliability and refining an experiment
Deformation of Solids
Thermal Physics
Topic overviewBoyle's law, Charles's law and the pressure lawThe ideal gas equation pV = nRTThe Avogadro constant, the mole and pV = NkTInternal energy and the distribution of molecular energyThe kinetic theory equation pV = ⅓Nm⟨c²⟩Average molecular kinetic energy and temperatureAbsolute zero and the kelvin scaleSpecific heat capacity and the electrical method
Uniform Circular Motion
Simple Harmonic Motion
Topic overviewDefining simple harmonic motion and a = −ω²xDisplacement, velocity and acceleration: x = A cos ωtThe simple pendulum and T = 2π√(l/g)The loaded spiral spring and T = 2π√(m/k)SHM graphs and finding velocity from a gradientFree vibrations, forced vibrations and resonanceDamping: light, critical and over-damping
The Nucleus and Radioactive Decay
Topic overviewAlpha-particle scattering and the nuclear atomNuclear radius and nucleon numberThe density of nuclear matterAlpha, beta and gamma radiation: nature, penetration and rangeNuclear equations and changes in nucleon and proton numberThe random and exponential nature of radioactive decayActivity, the decay constant and A = −λNExponential decay calculations with A = A₀e^(−λt)Half-life and measuring it
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Capacitors
- 9 subtopics
- 27 things to know
- Unit A2 2
What Capacitors covers
Capacitors is examined in Unit A2 2, Fields, Capacitors and Particle Physics, and drawn on again in Unit A2 3, Practical Techniques and Data Analysis. It covers capacitance and the farad, energy stored in a charged capacitor, capacitors in series and in parallel, charging and discharging a capacitor, the exponential decay equations, the time constant, flash guns and defibrillators, uses of capacitors in circuits and capacitor calculations and graph work.
Where it is assessed
Unit A2 2
Fields, Capacitors and Particle Physics, and again in Unit A2 3, Practical Techniques and Data Analysis.
Check the CCEA specification ↗The 9 subtopics
Each one has its own page.
- Capacitance and the faradCharge stored on a capacitor, construction of a simple capacitor and how a capacitor becomes charged when connected to a supply.Open →
- Energy stored in a charged capacitorRecall questions on E = ½QV and its two equivalent forms, why the factor of ½ appears, the energy as the area under a charge against potential difference graph, the fourfold rise when the voltage doubles, worked energy calculations, why only half the battery's energy is stored, and the defibrillator as a worked case.Open →
- Capacitors in series and in parallelRecall questions on the two combination rules and the reason for each in terms of shared charge or shared potential difference, why the rules are the opposite way round from resistors, worked calculations for both arrangements, which stores more charge at a given supply voltage, and finding the potential difference across each of a series pair.Open →
- Charging and discharging a capacitorExperiment to demonstrate the charging of a capacitor, how the discharge of a capacitor is demonstrated and shape of a graph of current against time during charging.Open →
- The exponential decay equationsRecall questions on the three decay equations for charge, potential difference and current with every symbol, what exponential decay means, worked calculations of the voltage after a stated time and of the time to reach a stated voltage, showing that equal intervals give equal fractional falls, and straightening the curve by plotting ln V against t.Open →
- The time constantRecall questions on the definition of the time constant as the time to fall to 1/e, τ = CR and the proof that the farad times the ohm gives the second, the fractions remaining after one, two and five time constants, worked calculations, the experiment to determine it, and why the voltmeter must have a very high resistance.Open →
- Flash guns and defibrillatorsTwo very different time constants involved in a flash gun and general principle these applications share.Open →
- Uses of capacitors in circuitsEffect of using too small a smoothing capacitor, working voltage of a capacitor and how it depends on the plate separation.Open →
- Capacitor calculations and graph workRecall questions combining charge, energy and time constant for a stated capacitor, what to plot for a gradient equal to the capacitance and what for the time constant, reading a time constant and an initial voltage off a logarithmic plot, comparing the energy stored in series and in parallel arrangements, and the half-life of a discharge as 0.69 CR.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Give the equation for the charge remaining on a discharging capacitor and define each symbol.
Key term
Define capacitance.
Key term
Give the equation for the energy stored in a charged capacitor in terms of charge and potential difference.
Key term
Describe an experiment to demonstrate the charging of a capacitor.
Key term
Give the equation for the time constant and define each symbol.
Key term
Explain the two very different time constants involved in a flash gun.
Key term
Why does a capacitor block direct current but pass alternating current?
Numbers
A 47 μF capacitor is charged to 24 V. Calculate the charge and the energy stored.
Key term
Give the defining equation for capacitance and define each symbol.
Key term
Why is the energy stored ½QV rather than QV?
Key term
Give the equation for capacitors connected in parallel.
Key term
Describe how the discharge of a capacitor is demonstrated.
Key term
Give the equation for the potential difference across a discharging capacitor
Key term
Show that the farad multiplied by the ohm gives the second.
Key term
Why is there a delay before a flash gun can be used again?
Key term
What decides how well a smoothing capacitor works?
Key term
What is plotted to obtain a straight line whose gradient is the capacitance?
Key term
Define the farad.
Key term
A 100 μF capacitor charged to 50 V stores 0.125 J by ½CV². Check that energy using the charge stored
Key term
Give the equation for capacitors connected in series.
Key term
Describe the shape of a graph of current against time during charging.
Key term
Give the equation for the current during the discharge of a capacitor
Key term
What fraction of the initial value remains after one time constant?
Numbers
A flash gun releases 67.5 J of stored energy in 2.0 ms. Calculate the average power
Key term
What is the effect of using too small a smoothing capacitor?
Key term
What is plotted to obtain a straight line whose gradient gives the time constant?
Take Capacitors further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
Define capacitance.
Model answer
Capacitance is the charge stored per unit potential difference across the capacitor.
- 2
Give the defining equation for capacitance and define each symbol.
Model answer
C = Q/V, where C is the capacitance in farads, Q the charge stored in coulombs and V the potential difference in volts.
- 3
Define the farad.
Model answer
One farad is the capacitance of a capacitor that stores one coulomb of charge for each volt of potential difference across it.
- 4
Why is the farad an inconveniently large unit?
Model answer
Storing a coulomb per volt is enormous for a practical component, so real capacitors are usually rated in microfarads, nanofarads or picofarads.
- 5
Express 470 μF in farads.
Model answer
470 × 10⁻⁶ F, which is 4.70 × 10⁻⁴ F.
- 6
What is meant by the charge stored on a capacitor?
Model answer
The magnitude of the charge on either plate, since one plate carries +Q and the other −Q and the capacitor as a whole is neutral.
What is inside Levo
Six ways to work the same material.
Capacitors revision questions
- What does Capacitors cover in CCEA A-Level Physics?
- 9 subtopics: capacitance and the farad, energy stored in a charged capacitor, capacitors in series and in parallel, charging and discharging a capacitor, the exponential decay equations, the time constant, flash guns and defibrillators, uses of capacitors in circuits and capacitor calculations and graph work. Each one has its own page with questions and model answers.
- How is Capacitors organised?
- By the CCEA 1210 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Capacitors, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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