Numbers
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
Electric Fields
Field strength calculations and combined fields
- 3 things to know
- Unit A2 2
Overview
Recall questions on the magnitude and direction of the field near a single negative charge, adding the fields of two like and two opposite charges at their midpoint and why the answers differ, balancing a charged oil drop against its weight, the acceleration of a proton in a uniform field, and accelerating a charge through a potential difference.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
A charge of −6.0 nC sits 0.15 m from a point. Calculate the magnitude of the field strength there.
Key term
A charge of −6.0 nC sits 0.15 m from a point. In which direction does the field at that point act?
Questions from this subtopic
Each one with the model answer underneath.
- 1
A charge of −6.0 nC sits 0.15 m from a point. Calculate the magnitude of the field strength there.
Model answer
E = 8.99 × 10⁹ × 6.0 × 10⁻⁹ ÷ 0.15², which is 54.0 ÷ 0.0225, giving 2.4 × 10³ N C⁻¹.
- 2
In which direction does that field point?
Model answer
Towards the charge, because the charge is negative and the field direction is that of the force on a positive test charge.
- 3
Two LIKE charges of 3.0 nC each are 0.40 m apart. Calculate the field strength at the midpoint.
Model answer
Each charge gives 8.99 × 10⁹ × 3.0 × 10⁻⁹ ÷ 0.20², which is 674 N C⁻¹, but the two point in opposite directions so the resultant is zero.
- 4
Two OPPOSITE charges of magnitude 3.0 nC are 0.40 m apart. Calculate the field strength at the midpoint.
Model answer
Each still gives 674 N C⁻¹, but now both point the same way, from the positive towards the negative charge, so the resultant is 1.3 × 10³ N C⁻¹.
- 5
An oil drop of weight 4.9 × 10⁻¹⁵ N is held stationary between plates giving a field of 3.0 × 10⁴ V m⁻¹. Calculate the charge on it.
Model answer
The electric force balances the weight, so q = F/E = 4.9 × 10⁻¹⁵ ÷ 3.0 × 10⁴, which is 1.6 × 10⁻¹⁹ C.
- 6
Which way must the field point for the drop to be held up, given the drop is negatively charged?
Model answer
Downwards, so that the force on the negative charge is upwards and opposes the weight.
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