Formulae

Power = Current x Voltage 

Energy = Power x time

Charge = Current x time

Voltage = Current x Resistance

Ohm's Law:

The current that flows through a conductor is directly proportional to the p.d. across its ends. (provided temperature stays constant)

Frequency = 1 / Time Period

Wave Speed (m/s) = Frequency(Hz) x Wavelength(m)

Refractive Index = sin i / sin r

sin c = 1 / n