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
Internal Resistance and Potential Dividers
Measuring electromotive force and internal resistance
- 3 things to know
- Unit AS 1
Overview
Recall questions on the apparatus and method, what is plotted against what, the shape of the graph and why it is a straight line, what the intercept and the gradient each represent, a worked determination, the simpler two-reading method and why it is less reliable, and why the voltmeter must have a high resistance.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
When measuring the electromotive force and internal resistance of a cell, why should the current be kept modest and the circuit switched off between readings?
Key term
Outline the method used to determine the electromotive force and internal resistance of a cell.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the apparatus needed to determine the electromotive force and internal resistance of a cell.
Model answer
The cell under test, a variable resistor or a set of fixed resistors to act as the load, an ammeter in series, a high-resistance voltmeter across the cell's terminals, a switch and connecting leads.
- 2
Outline the method used to determine the electromotive force and internal resistance of a cell.
Model answer
Connect the cell to the load through the ammeter with the voltmeter across the terminals, then for each of several settings of the variable resistor close the switch, record the current and the terminal potential difference, and plot the results.
- 3
Which quantities are plotted against each other in this determination, and on which axes?
Model answer
The terminal potential difference is plotted on the vertical axis against the current on the horizontal axis.
- 4
Describe the shape of the graph obtained in this experiment.
Model answer
It is a straight line of negative gradient, sloping downwards from an intercept on the potential difference axis as the current increases.
- 5
What does the intercept on the potential difference axis represent in this experiment?
Model answer
The intercept at zero current is the electromotive force of the cell, because with no current there are no lost volts.
- 6
What does the gradient of the graph represent in this experiment?
Model answer
The gradient is −r, so the internal resistance is the magnitude of the gradient, measured in ohms.
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