What does the CCEA A2 2 unit cover?

A2 2 is the synoptic A2 unit. It covers electric fields with Coulomb's law, field strength and potential and the parallels with gravity, capacitors with capacitance, energy stored, series and parallel combinations and exponential charging and discharging, magnetic fields with the force on a conductor and a moving charge, flux and flux linkage and electromagnetic induction governed by Faraday's and Lenz's laws, particle physics with quarks, leptons, hadrons, antiparticles and conservation laws, and astronomy and cosmology with stellar measurement, redshift, Hubble's law and the evidence for the Big Bang.

How are electric and gravitational fields similar and different?

Both the electric and gravitational forces obey an inverse-square law with distance, both define a field strength as force per unit charge or mass, and both have a potential that follows an inverse law with distance. The key difference is that the gravitational force is always attractive, so masses cannot be shielded, whereas the electric force can be attractive or repulsive depending on the signs of the charges, and conductors can shield electric fields.

Why do capacitors combine in the opposite way to resistors?

For capacitors in parallel the plate areas effectively add, so the capacitances add directly, while in series the same charge sits across a larger total separation, so the reciprocals add. Resistors do the opposite: they add directly in series and combine by reciprocals in parallel. It is worth memorising the two pairs of rules separately to avoid mixing them up in the exam.

What is the most common mistake in A2 2?

Frequent errors include assuming the electric force is always attractive, using the resistor rules for capacitors, applying the right-hand rule to the motor effect when the force on a current uses the left hand, calling leptons hadrons, and saying redshift means galaxies move away from a centre rather than space itself expanding. Careful use of signs, the correct hand rule and the conservation laws avoids most of these.

How should I revise the A2 2 unit?

Work topic by topic against the specification statements. Drill Coulomb's law and field calculations and compare fields with gravity, practise capacitance, energy and exponential decay problems with the time constant, and rehearse the motor effect, flux linkage and Faraday's and Lenz's laws. Learn the quark and lepton classifications and the conservation laws, and practise redshift and Hubble's law calculations along with the evidence for the Big Bang.

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CCEA A-Level Physics A2 2 Fields, Capacitors, Particles and Astronomy: a complete overview of fields, capacitance, particle physics and cosmology

A deep-dive CCEA A-Level Physics guide to the A2 2 unit on electric fields, capacitors, magnetic fields and electromagnetic induction, particle physics and the standard model, and astronomy and cosmology. Covers Coulomb's law, capacitance and exponential decay, the motor effect, Faraday's and Lenz's laws, quarks and leptons, and redshift and the Big Bang, with the equations CCEA examines.

Generated by Claude Opus 4.818 min readCCEAUpdated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

What this unit demands
Electric fields and capacitors
Magnetic fields and induction
Particle physics
Astronomy and cosmology
How this unit is examined
Check your knowledge

What this unit demands

A2 2 is the synoptic finish to the course, bringing together the field concept, capacitance, the fundamental constituents of matter and the structure and history of the universe. The examiners test precise definitions, confident calculation across fields, capacitors and induction, and clear application of the conservation laws and the cosmological evidence.

This guide walks through the five dot points of the unit, then sets out the exam patterns CCEA repeats. Each topic has a matching dot-point page with practice questions; this overview ties them together.

Electric fields and capacitors

Coulomb's law gives the force between charges, the field strength is force per unit charge ( $\frac{V}{d}$ between plates), and the potential is energy per unit charge. Electric and gravitational fields share inverse-square laws, but gravity is only attractive. A capacitor stores charge $Q = CV$ and energy $\tfrac{1}{2}CV^2$ ; capacitors add in parallel and combine by reciprocals in series, and discharge exponentially with time constant $RC$ .

Magnetic fields and induction

A current in a field feels a force $F = BIL$ and a moving charge feels $F = Bqv$ , both by Fleming's left-hand rule. Magnetic flux is $\Phi = BA$ and flux linkage is $N\Phi$ . Faraday's law gives the induced e.m.f. as the rate of change of flux linkage, and Lenz's law says the induced current opposes the change, a consequence of conservation of energy.

Particle physics

Matter is built from quarks and leptons. Hadrons are baryons (three quarks) or mesons (a quark and an antiquark); leptons are fundamental. Every particle has an antiparticle of opposite charge, and a particle meeting its antiparticle annihilates into photons. Interactions conserve charge, baryon number and lepton number.

Astronomy and cosmology

Stellar distances come from luminosity and parallax. Galaxy light is redshifted, giving recession speed through $\frac{\Delta\lambda}{\lambda} = \frac{v}{c}$ . Hubble's law $v = H_0 d$ shows the universe is expanding, implying the Big Bang, supported by the cosmic microwave background and the hydrogen-helium abundance.

How this unit is examined

A typical CCEA profile for A2 2:

Definitions. Field strength and potential, capacitance, flux linkage, and the quark and lepton classifications.
Calculation. Coulomb's law, field strength, capacitor energy and exponential decay, the motor effect, and redshift.
Conservation. Checking particle interactions against charge, baryon and lepton number.
Evidence. Explaining redshift, Hubble's law and the support for the Big Bang.

Check your knowledge

A mix of recall and calculation questions covering the unit. Attempt them under timed conditions, then check against the solutions.

State one similarity and one difference between electric and gravitational fields. (2 marks)
Two parallel plates $5.0\,\text{mm}$ apart have a potential difference of $200\,\text{V}$ . Find the field strength. (2 marks)
A $50\,\mu\text{F}$ capacitor is charged to $9.0\,\text{V}$ . Find the energy stored. (2 marks)
A $100\,\mu\text{F}$ capacitor discharges through a $20\,\text{k}\Omega$ resistor. Find the time constant. (2 marks)
State Faraday's law and Lenz's law of electromagnetic induction. (2 marks)
State the quark composition of a proton and a neutron. (2 marks)
Name two quantities that are conserved in particle interactions. (2 marks)
State Hubble's law and what it implies about the universe. (2 marks)

Solutions

Q1: Both forces follow an inverse-square law with distance (similarity); gravity is always attractive, but the electric force can be attractive or repulsive depending on the charges (difference).
Q2: $E = \frac{V}{d} = \frac{200}{5.0 \times 10^{-3}} = 4.0 \times 10^{4}\,\text{V}\,\text{m}^{-1}$ .
Q3: $E = \tfrac{1}{2}CV^2 = \tfrac{1}{2}(50 \times 10^{-6})(9.0)^2 = 2.0 \times 10^{-3}\,\text{J}$ .
Q4: $\tau = RC = (20 \times 10^{3})(100 \times 10^{-6}) = 2.0\,\text{s}$ .
Q5: Faraday's law: the induced e.m.f. equals the rate of change of flux linkage. Lenz's law: the induced current opposes the change that produces it (conservation of energy).
Q6: Proton is up, up, down (uud); neutron is up, down, down (udd).
Q7: Any two of: charge, baryon number, lepton number (also energy and momentum).
Q8: A galaxy's recession speed is proportional to its distance, $v = H_0 d$ ; this implies the universe is expanding from a hot, dense beginning, the Big Bang.

Sources & how we know this

CCEA GCE Physics specification — CCEA (2016)