# Electrical Energy Calculations Tutorial

## Key Concepts

- The electrode potential of a galvanic (voltaic) cell, or a battery while it is discharging, is an EMF or voltage.
- This voltage (EMF) produced by the cell or battery can be used to calculate the electrical energy delivered by that cell or battery.
- The electrolysis of a substance requires an input of electrical energy.
This electrical energy can be used to :

(i) recharge a battery (eg, recharge a lead-acid battery)

(ii) electroplate an object

(iii) extract a metal from its ore

- Electrical energy, E, measured in joules (J) produced by a battery, or used during electrolysis, can be calculated:
E = Q × V

E = energy in joules (J)

Q = quantity of electricity or charge in coulombs (C)

V = voltage (or EMF) in volts (V)

- Rearranging this equation allows us to calculate:
(i) quantity of electricity (charge):

Q = E ÷ V(ii) voltage (emf):

V = E ÷ Q - The kilowatt-hour, kWH, is a unit of electrical energy.
1 kWH = 3.6 x 10

^{6}JTo convert energy in joules to kWh, divide energy in joules by 3.6 x 10

^{6}.To convert energy in kilo-watt hours to joules, multiply kWh by 3.6 x 10

^{6}.