Unit 3: Field and Potential

This Nuffield Advanced Physics unit was concerned with the ideas of field and potential, developed for the electric and the gravitational fields. A main aim was to suggest that ideas about field and potential are rather general and so very useful. Their generality and usefulness were brought out in the unit by switching attention from the uniform electric field in Part One to the gravitational field in Part Two, and back to the electric field of a point charge in Part Three.

Contents of the Students’ book
*To the student
*Summary of Unit
*Questions
Part One: The uniform electric field
Part Two: Gravitational field and potential
Part Three: The electrical inverse square law
Part Four: Ionic crystals
*Answers
*Ionic crystals
*Thunderstorms
*Feynman on gravity
*Books for Unit 3
*Formulae, data, and circuit symbols

Experiments suggested for the Unit
3.1: The shuttling ball
3.2: Force on a charged strip of foil
Optional: Uniform field (Millikan apparatus)
3.3: Electric field patterns
3.4: Reed switch and a parallel plate capacitor
3.5: Electrometer and parallel plate capacitor
3.6: Test of reed switch; capacitors in series and in parallel
3.7: Measurement of the permittivity of a vacuum
3.8: Flame probe investigation of voltages in a parallel plate capacitor
3.9: Measurement of the gravitational force constant G
3.10: Ball rolling on a 1/r shaped hill

3.11: Flame probe investigation of the potential around a charged sphere
3.12: Measurement of the constant of proportionality in ‘V proportional to Q/r’

3.13: Tests of Coulomb's Law
Optional: Force on a hanging ball pulled sideways