Physics·Electricity and magnetism · NSSCO 5.4
Electrical energy & power
Narrated lesson · press play
Every appliance you switch on turns electrical energy into something useful — and it does it at a certain rate, called power. This lesson builds electrical power from the ground up: P = V I and P = I²R, then electrical energy E = P t and E = V I t, then the kilowatt-hour on your bill, and finally the part everyone loves — working out exactly what it costs to run real appliances at home.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 5.4):
- Define electrical power as the rate at which electrical energy is transferred, measured in the watt (W)
- Recall and use the equation power = voltage × current (P = V I), and also P = I²R
- Recall and use the equations energy = power × time (E = P t) and energy = voltage × current × time (E = V I t)
- Interpret the power rating of bulbs, lamps and other electrical appliances
- Understand energy consumption measured in kilowatt-hours (kWh)
- Calculate the cost of using electrical appliances where the unit is the kWh
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Ms Elizabeth and Mike talk through the whole topic — with the figure and working drawn live.