What does the Edexcel Fields and their consequences module cover?

It covers electric fields with Coulomb's law, field strength and potential, capacitance with the energy stored and exponential charge and discharge through a resistor, magnetic flux density and the motor effect with the force on a moving charge, magnetic flux and flux linkage with Faraday's and Lenz's laws, and gravitational fields with Newton's law of gravitation, field strength, potential and orbital motion.

Which equations recur most across this module?

Coulomb's law $F = \frac{1}{4\pi\varepsilon_0}\frac{Q_1 Q_2}{r^2}$, field strengths $E = \frac{V}{d}$ and $g = \frac{GM}{r^2}$, capacitance $C = \frac{Q}{V}$ with energy $\frac{1}{2}CV^2$ and discharge $Q = Q_0 e^{-t/RC}$, the motor-effect force $F = BIL$ and $F = Bqv$, Faraday's law $\varepsilon = \frac{\Delta(N\Phi)}{\Delta t}$, and Newton's law of gravitation $F = \frac{GMm}{r^2}$.

How are electric and gravitational fields similar and different?

Both are inverse-square fields, so field strength falls as $\frac{1}{r^2}$ and potential as $\frac{1}{r}$, and the orbit and force mathematics look the same. The key difference is that gravity is always attractive, so gravitational potential is always negative, whereas electric forces can attract or repel and electric potential can be positive or negative.

What is the most common mistake in this module?

Forgetting the factor of one half in the capacitor energy, $\frac{1}{2}CV^2$, which arises because the voltage builds up during charging. Other frequent errors are using flux instead of flux linkage in Faraday's law, making gravitational potential positive, and confusing the radial field formula with $E = \frac{V}{d}$ for parallel plates.

How should I revise Fields and their consequences?

Treat the three fields together, comparing their inverse-square structure. Drill capacitor energy and exponential discharge with the time constant, and the induction calculation using flux linkage and rate of change. Practise orbit problems by equating gravitational and centripetal force, and keep the sign conventions for potential clear.

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Edexcel A-Level Physics Fields and their consequences: a complete overview of electric, magnetic and gravitational fields and capacitance

A deep-dive Edexcel A-Level Physics guide to Fields and their consequences. Covers electric fields and Coulomb's law, capacitance and exponential discharge, magnetic fields and electromagnetic induction, and gravitational fields and orbits, with the calculations and exam patterns Edexcel repeats.

Generated by Claude Opus 4.818 min read9PH0Updated 2026-06-02

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

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What this module actually demands
Electric fields and capacitance
Magnetic and gravitational fields
How this module is examined
Check your knowledge

What this module actually demands

Fields and their consequences treats the three fundamental fields together. It develops electric fields and capacitance, then magnetic fields and electromagnetic induction, then gravitational fields and orbits, drawing out the deep parallels between them. The examiners reward recognising the common inverse-square structure, careful sign conventions, and confident handling of exponential discharge and induction calculations.

This guide walks through the topics in order and sets out the exam patterns Edexcel repeats. Each topic has a matching dot-point page; this overview ties them together.

Electric fields and capacitance

Electric fields uses Coulomb's law, defines field strength ( $E = \frac{V}{d}$ for plates, $\frac{1}{4\pi\varepsilon_0}\frac{Q}{r^2}$ radial) and electric potential, and analyses charged particles in uniform fields as parabolic motion. Capacitance defines $C = \frac{Q}{V}$ , gives the energy stored as $\frac{1}{2}CV^2$ , and develops the exponential charge and discharge of a capacitor through a resistor with the time constant $\tau = RC$ .

Magnetic and gravitational fields

Magnetic fields and induction defines magnetic flux density through $F = BIL$ , gives the force on a moving charge $F = Bqv$ , defines flux and flux linkage, and applies Faraday's and Lenz's laws. Gravitational fields applies Newton's law of gravitation, defines field strength and potential, and analyses circular orbits by equating gravitational and centripetal force, leading to Kepler's third law.

How this module is examined

A typical Edexcel profile:

Calculations. Coulomb force, field strength and potential, capacitor energy and time constant, exponential discharge, induced EMF from flux linkage, and orbital speed and period.
Graph questions. Capacitor discharge curves and log-linear plots, field-line and equipotential diagrams.
Explanation. Lenz's law and energy conservation, why gravitational potential is negative, and the analogy between electric and gravitational fields.
Extended answers. Charged-particle deflection, the operation of a simple generator, and satellite orbit analysis.

Check your knowledge

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

Define electric field strength. (1 mark)
Two plates $4.0$ cm apart have a $200$ V potential difference. Find the field strength. (1 mark)
A $220$ uF capacitor is charged to $9.0$ V. Find the energy stored. (2 marks)
State Faraday's law of electromagnetic induction. (1 mark)
A capacitor discharges through a resistor with time constant $2.0$ s. After how long does the charge fall to about $37\%$ of its initial value? (1 mark)
Explain why gravitational potential is always negative. (2 marks)

Sources & how we know this

Pearson Edexcel A-Level Physics (9PH0) specification — Pearson Edexcel (2015)