Key term
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
Thermal Physics
The kinetic theory equation pV = ⅓Nm⟨c²⟩
- 3 things to know
- Unit A2 1
Overview
Mean square speed of the molecules of a gas, root mean square speed and how the kinetic theory equation accounts for Boyle's law.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Explain how the kinetic theory equation accounts for Boyle's law.
Key term
At the same temperature, how do the root mean square speeds of hydrogen and oxygen molecules compare?
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the kinetic theory equation for the pressure of an ideal gas and define every symbol.
Model answer
pV = ⅓Nm⟨c²⟩, where p is the pressure in Pa, V the volume in m³, N the number of molecules, m the mass of one molecule in kg and ⟨c²⟩ the mean square speed of the molecules in m² s⁻².
- 2
What is meant by the mean square speed of the molecules of a gas?
Model answer
The mean square speed is the average of the squares of the individual molecular speeds, measured in m² s⁻².
- 3
What is meant by the root mean square speed, and how is it obtained from the mean square speed?
Model answer
The root mean square speed is the square root of the mean square speed, √⟨c²⟩, measured in m s⁻¹, and it is a typical molecular speed for the sample.
- 4
State three assumptions made about the molecules in deriving the kinetic theory equation.
Model answer
The molecules are in continual random motion, their collisions with each other and with the walls are perfectly elastic, and the volume of the molecules themselves is negligible compared with the volume of the container.
- 5
State two further assumptions of kinetic theory concerning the forces on molecules and the duration of collisions.
Model answer
There are no intermolecular forces except during collisions, and the time spent in a collision is negligible compared with the time between collisions.
- 6
Write the kinetic theory equation in the form that uses the density of the gas.
Model answer
Since the total mass Nm divided by V is the density ρ, the equation becomes p = ⅓ρ⟨c²⟩, with ρ in kg m⁻³ and p in Pa.
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