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 electric motor
- 3 things to know
- Unit A2 2
Overview
Principle on which an electric motor works, effect of those two opposite forces and four ways of increasing the turning effect of a motor.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Why do the two sides of a rectangular coil experience forces in opposite directions?
Key term
Give the equation for the force on one side of a coil of N turns.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is the principle on which an electric motor works?
Model answer
A current-carrying coil in a magnetic field experiences forces on its sides that produce a turning effect, so the coil rotates.
- 2
Why do the two sides of a rectangular coil experience forces in opposite directions?
Model answer
The current flows in opposite directions along the two sides, and the field is the same, so Fleming's left-hand rule gives opposite forces.
- 3
What is the effect of those two opposite forces?
Model answer
They form a couple, producing a turning moment about the axis of the coil without any resultant force on it.
- 4
Give the equation for the force on one side of a coil of N turns.
Model answer
F = BINl, where N is the number of turns, since each turn carries the current through the field.
- 5
Name four ways of increasing the turning effect of a motor.
Model answer
Increase the current, increase the number of turns on the coil, use a stronger magnetic field, and increase the area of the coil.
- 6
What is the purpose of the split-ring commutator?
Model answer
It reverses the current in the coil every half turn, so the forces keep turning the coil the same way instead of reversing at the vertical position.
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