a) Charge

a) electric current as rate of flow of charge; I = ∆Q/∆t

b) the coulomb as the unit of charge

c) the elementary charge e equals 1.6×10^-19C

d) net charge on a particle or an object is quantised and a multiple of e

current = rate of flow of charge (coulombs of charge that pass a point in a circuit per second)

I = Q/t

• current (A) = charge passing a point in a circuit (C) / time taken for charge to pass the point (s)

one coulomb of charge → contains many electrons/protons

• elementary charge of each electron/proton = ±1.6×10^-19C

  • charge of a charged object → multiple of elementary charge

  • so charge is quantised

• relative charge → measured against elementary charge

  • ±1e = ±1.6×10^-19C

• Q = ±ne

• net charge of an object (C) = number of electrons lost or gained × elementary charge (C)