1.1 We often use electrical appliances because they transfer energy
at the flick of a switch. We can calculate how much energy is
transferred by an appliance and how much the appliance costs to
run.
1.1.1 The amount of electrical energy transferred to an appliance
depends on its power and the length of time it is switched on. The
amount of mains electrical energy transferred is measured in
kilowatt-hours, kWh. One unit is 1 kWh.
1.1.1.1 E = P × t where E is
the energy transferred
in kilowatt-hours, kWh,
P is the power in
kilowatts, kW and T is
the time in hours, h.
1.1.1.1.1 You can also use the equation E = P × t when E is the energy transferred in joules,
J, P is the power in watts, W and T is the time in seconds, s.
1.1.1.1.1.1 Electricity meters measure the number of units
of electricity used in a home. The more units
used, the greater the cost. The cost of the
electricity used is calculated using this
equation: total cost = number of units × cost
per unit.