Subject 20 · Electricity & Magnetism
Chapter 20
Electricity & Magnetism
Follow energy from electric fields through wires and cells, into heating and magnetic effects, and finish with motor action, calculus, and mains safety.
Build electricity & magnetism one idea at a time.
Start with the foundations, then explore advanced ideas and calculus at the depth your course needs.
7 of 7 lessons
Fields Driving Current
Connect internal electric field, potential difference, and drift velocity.
The Heating Effect
Analyse appliances, cables, energy cost, fuses, and non-ohmic filaments.
Electric Cells
Separate e.m.f. from terminal voltage and model capacity and discharge.
Magnetic Effects of Currents
Use right-hand rules for wires, solenoids, electromagnets, and relays.
The Motor Effect
Combine field, current, force direction, and commutation.
Electricity & Magnetism Calculus
Recover charge, energy, and force from changing electrical quantities.
Electrical Safety
Explain live, neutral, earth, fuses, double insulation, and RCDs.
Change one variable. Watch the physics respond.
Explore Pload = εI − I²r, then take the idea into the full lessons.
Find a cell's power sweet spot
Cell e.m.f. fixed at 12 V. Internal resistance turns part of the cell's power into heat.
Everything around the chapter, in one place.
Keep building with practice, classroom presentations, formulae, and a game that puts these ideas to work.
Exam practice
Questions, guided reasoning, and exam-style problem solving.
Browse exam questions →Formula toolkit
Keep the key relationships and their units close to hand.
Review formulae →Members · Classroom presentationClassroom slides
Reveal lesson ideas, examples, and checks in full-screen classroom mode.
Open slides →Lesson files
Find downloadable teaching resources and worksheets in the library.
View files →Cell Rover
P = εI − I²r. Choose current draw so one battery carries a rover through every stage.
Play the free chapter game →See it. Read it. Work it.
Connect diagrams to physical relationships and exam reasoning.
Explore diagrams →Guided support
Ask for a hint, check your reasoning, or explore a similar problem.
Ask GioAI →Key ideas to remember
Move without losing your place.
Extra challenging questions
Take the ideas further with course-specific extension questions, supplied-data graphs and worked solutions.