Electric Charges and Fields

Coulomb's law (1.5): name the 4 key ideas

• F = kq₁q₂/r² • k = 1/4πε₀ • Vector form • Electric vs gravitational force

Explain why: “F = kq₁q₂/r²”

The scalar form used in most numericals.

What do these mean: start on positive, end negative?

Lines leave positive charges and enter negative ones.

Field lines (1.8): name the 4 key ideas

• Start on positive, end negative • Never cross • Density shows strength • Diagrams to draw

Explain why: “p = q × 2a”

Dipole moment points from the negative to the positive charge.

What is charging by rubbing?

Glass rubbed with silk turns positive while amber rubbed with wool turns negative.

Electric dipole (1.10): name the 4 key ideas

• p = q × 2a • Axial field • Equatorial field • Polar molecules (1.10.2)

What is additivity (1.4.1)?

Total charge is the plain algebraic sum of all charges present.