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
Capacitor calculations and graph work
- 3 things to know
- Unit A2 2
Overview
Recall 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.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is plotted to obtain a straight line whose gradient is the capacitance?
Key term
What is plotted to obtain a straight line whose gradient gives the time constant?
Questions from this subtopic
Each one with the model answer underneath.
- 1
A 47 μF capacitor is charged to 24 V. Calculate the charge and the energy stored.
Model answer
Q = CV = 47 × 10⁻⁶ × 24 = 1.13 × 10⁻³ C, and E = ½QV = 0.5 × 1.13 × 10⁻³ × 24 = 1.4 × 10⁻² J.
- 2
What is plotted to obtain a straight line whose gradient is the capacitance?
Model answer
Charge stored on the vertical axis against potential difference on the horizontal axis.
- 3
How is the energy stored obtained from a charge against potential difference graph?
Model answer
It is the area between the line and the horizontal axis up to the potential difference to which the capacitor is charged.
- 4
What is plotted to obtain a straight line whose gradient gives the time constant?
Model answer
The natural logarithm of the potential difference on the vertical axis against time on the horizontal axis.
- 5
A discharge graph of ln V against t has a gradient of −0.25 s⁻¹ and an intercept of 2.30. Find the time constant and the initial voltage.
Model answer
The time constant is 1 ÷ 0.25 = 4.0 s, and the initial voltage is e^(2.30), which is 10 V.
- 6
Two capacitors of 100 μF and 100 μF are charged in parallel to 20 V. Calculate the total energy stored.
Model answer
The total capacitance is 200 μF, so E = 0.5 × 200 × 10⁻⁶ × 20² = 0.040 J.
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