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
Current, Charge and Potential Difference
Electromotive force
- 3 things to know
- Unit AS 1
Overview
Recall questions on the definition and the energy-per-unit-charge equation, why the name is misleading, four sources and the energy conversion each performs, cells in series and in opposition, cells in parallel, what a high-resistance voltmeter reads on an open circuit, and calculations of energy transferred.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Name four sources of electromotive force and state the energy conversion each carries out.
Numbers
A 1.5 V cell drives a steady current of 0.20 A for 30 minutes. Calculate the total energy it converts into electrical energy.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define electromotive force.
Model answer
The electromotive force of a source is the energy converted from other forms into electrical energy per unit charge driven through the source.
- 2
State the equation for electromotive force in terms of energy and charge, and give the unit.
Model answer
The electromotive force is E = W/Q, where W is the energy converted into electrical energy in joules and Q is the charge in coulombs, so E is measured in volts.
- 3
Why is the name electromotive force misleading?
Model answer
It is not a force at all but an energy transferred per unit charge, so it is measured in volts rather than in newtons.
- 4
Name four sources of electromotive force and state the energy conversion each carries out.
Model answer
A chemical cell converts chemical energy, a dynamo converts kinetic energy, a thermocouple converts internal energy from a temperature difference and a solar cell converts light energy, and each converts its input into electrical energy.
- 5
A cell of electromotive force 1.5 V drives a charge of 400 C round a circuit. Calculate the energy converted into electrical energy.
Model answer
The energy is W = EQ = 1.5 × 400 = 6.0 × 10² J, and 600 J ÷ 400 C returns the 1.5 V electromotive force as a check.
- 6
A battery converts 2700 J of chemical energy into electrical energy while a charge of 300 C passes through it. Calculate its electromotive force.
Model answer
The electromotive force is E = W/Q = 2700 ÷ 300 = 9.0 V, and 300 C × 9.0 V gives back 2700 J as a check.
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