Electrical Energy Calculations Tutorial
- 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 106 J
To convert energy in joules to kWh, divide energy in joules by 3.6 x 106.
To convert energy in kilo-watt hours to joules, multiply kWh by 3.6 x 106.