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
Magnetic Fields
The alternating current generator
- 3 things to know
- Unit A2 2
Overview
Recall questions on the construction and how it differs from a motor in using slip rings rather than a commutator, why rotating the coil induces an electromotive force, E = BANω sinωt and the peak value BANω, where in the rotation the electromotive force is greatest and where zero, the sine output, and the ways of increasing the peak value.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Give the equation for the e.m.f. produced by a rotating coil and define each symbol.
Key term
Why does rotating the coil induce an e.m.f.?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe the basic construction of a simple a.c. generator.
Model answer
A coil of many turns is rotated in a magnetic field between the poles of a magnet, with the ends of the coil connected to slip rings and brushes.
- 2
How does an a.c. generator differ in construction from a d.c. motor?
Model answer
The generator uses slip rings, which keep each end of the coil connected to the same terminal, while the motor uses a split-ring commutator that swaps them every half turn.
- 3
Why does rotating the coil induce an e.m.f.?
Model answer
The flux linkage through the coil changes continuously as it turns, and by Faraday's law a changing flux linkage induces an e.m.f.
- 4
Give the equation for the e.m.f. produced by a rotating coil and define each symbol.
Model answer
E = BANω sinωt, where B is the flux density in tesla, A the coil area in square metres, N the number of turns, ω the angular velocity in rad s⁻¹ and t the time in seconds.
- 5
Give the expression for the peak e.m.f. of a rotating-coil generator.
Model answer
The peak e.m.f. is BANω. That value is reached whenever sinωt equals one.
- 6
At which position of the coil is the induced e.m.f. greatest?
Model answer
When the plane of the coil is parallel to the field, because the sides are then cutting the field lines at the greatest rate.
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