Electrostatics

Electric Charge

Fundamental property of matter

Electricness of particles

Coulomb

e = 1.6 × 10^-19 C

Elementary charge of one electron

Properties of Charge

Quantized - only integer multiples of e

Conserved - no net charge created or destroyed: invariant

Law of Conservation of Charge

Net charge in an isolated system is constant

Insulators

Materials where charges don’t move freely

Electrons tightly bound around nuclei

Conductors

Materials where electrons move freely

Coulomb’s Law

F_e = k |Q₁Q₂| / r²

k = 8.99 × 10⁹ Nm²/ C²

Attractive and repulsive forces

Newton’s law of universal gravitation

F_g = GmM / r²

G = 6.11 × 10^-11 Nm² / kg²

Only attractive forces

Electric field lines

1. Begin on a positive charge and end on negative

2. Proximity = strength

3. E lines from one source never intersect

Semiconductor

Between insulator and conductor

Superconductor

0 electrical resistance below certain temp.

Charging by Friction

Rubbing 2 insulating materials together

Only electrons move

Charging by contact

Physical contact of charged object w/ neutral object

Charging by Induction

Give charge w/o touching object via polarization

• Movement of electrons from grounding in response to charged object

Separate object into positive and negative sides

Proton Mass

1.67 × 10^-27 kg

Electron mass

9.11 × 10^-31 kg