Unit 7: Magnetic Fields

This Nuffield Advanced Physics Unit was designed to be directly about engineering
problems and their solution. The authors pointed out that ‘reluctance’, like feedback in Unit 6, is a concept of more use to an engineer than to a physicist. The authors said that they made no apology for abandoning the physicist's point of view in some parts of three Units in the course; it was well enough represented elsewhere. They argued that to look at things in only that one way would be to ignore the variety of interests among students.

Much of the Unit followed well trodden paths. Part Two contained a careful development of electromagnetic induction, which, while being treated with as practical a slant as possible and emphasizing ideas which was planned to be of value. Part Three turned mainly around rates of change, turns, flux, and the idea of linking where the engineer's and the physicist's interests largely coincide.

Contents of the Students’ book
*To the student
*Summary of Unit 7
*Questions
Part One: Forces on currents
Part Two: Electromagnetic induction
Part Three: Flux near currents
*Answers
*Induction motors
*The generation and transmission of power
*Railway electrification
*Further reading
*Data and formulae

Experiments suggested for the Unit
7.1 Electromagnetic forces
7.2 Shapes of magnetic fields
7.3 Measuring magnetic fields page 17
7.4 The Hall effect, and using it to measure magnetic fields
7.5 The Hall effect in aluminium (number of charge carriers per atom)
7.6 Measurement of the charge to mass ratio for electrons
7.7 Behaviour and energy balance of a direct current motor dynamo
7.8 Making a motor into a dynamo
7.9 Moving wires and changing fields
7.10 The law of electromagnetic induction
7.11 Investigations of transformer action
7.12 Self-induction
7.13 Fields around electric currents
7.14 Ampere's Law
7.15 Absolute measurement of current (and other electrical quantities)
7.16 Eddy currents
7.17 Induction motors