The unit in one line
Charge on the move: what drives it round a circuit, what it does to the instruments we measure it with, and the magnetism it creates and answers to. 9 of Physics's 50 questions over seven chapters.
The chapters
| Chapter | What it covers | Read |
|---|---|---|
| Electrical quantities | Current and drift velocity, Ohm's and Joule's laws, resistance and resistivity, emf against potential difference, and electrical energy and power | 15 min |
| Electrical circuits | Kirchhoff's laws and resistor combinations, the Wheatstone bridge, metre bridge and potentiometer, and the galvanometer turned into an ammeter or a voltmeter | 19 min |
| Thermoelectric effect | The Seebeck and Peltier effects, neutral and inversion temperatures, and thermocouple calculations | 14 min |
| Alternating currents | Peak and rms values, phase, impedance, power and Q-factor in LRC circuits, resonance, and rectification by a diode bridge | 16 min |
| Magnetic properties of materials | Domains, relative permeability and susceptibility, the diamagnetic, paramagnetic and ferromagnetic classes, and the hysteresis loop | 16 min |
| Magnetic field | The field of a straight conductor, a circular coil and a long solenoid, the force on a moving charge and on a current-carrying conductor or coil, and the Hall effect | 17 min |
| Electromagnetic induction | Faraday's and Lenz's laws, the AC generator, the transformer and eddy currents, and self and mutual inductance | 18 min |
About two hours in all.
Read in this order
Start with electrical quantities and then electrical circuits: the second chapter is the first one applied, and every bridge and meter in it is an argument about potential difference.
The ordering that actually matters comes later. Alternating currents sits fourth in the syllabus but depends on the last two chapters, because the opposition an inductor offers to a changing current is induction in disguise. Read magnetic field and then electromagnetic induction before you open alternating currents, and impedance stops being a formula to memorise. Magnetic field must come before induction in any case: flux is the field counted through an area.
Thermoelectric effect and magnetic properties of materials are self-contained and can be read at any point. Both are short, heavily factual and easy marks, so do not leave them unread on the assumption that they are minor.
How it is asked
MEC sets the paper roughly half recall, a third understanding and a fifth application. Recall here is a unit, a law, or which material is diamagnetic. Understanding is why a potentiometer measures emf where a voltmeter cannot, why the shunt goes in parallel, or why a transformer will not run on direct current. Application is one substitution: an equivalent resistance, a balanced bridge, an rms value, a transformer ratio, or the force on a wire.
Then practise
Each chapter has a fixed-length chapter test under Practice › Topics, drawn from questions written to that chapter's scope.