Module 4: Electrons, waves and photons

4.1 Charge and current

4.1.1 Charge	(a) electric current as rate of flow of charge; I = ΔQ/Δt
	(b) the coulomb as the unit of charge
	(c) the elementary charge e equals 1.6 × 10^–19 C	You will be expected to know that an electron has charge –e and a proton a charge +e.
	(d) net charge on a particle or an object is quantised and a multiple of e
	(e) current as the movement of electrons in metals and movement of ions in electrolytes
	(f) conventional current and electron flow
	(g) Kirchhoff's first law; conservation of charge.
4.1.2 Mean drift velocity	(a) mean drift velocity of charge carriers
	(b) I = Anev, where n is the number density of charge carriers
	(c) distinction between conductors, semiconductors and insulators in terms of n.