Electrical Power and Energy
Electrical power is the rate at which a device transfers energy, equal to the voltage multiplied by the current.
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Electrical power is the rate at which a device transfers energy, equal to the voltage multiplied by the current.
- P equals V times I
- Energy equals power times time
- The kilowatt-hour is the unit on electricity bills
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Electrical Power and Energy?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Electrical Power and Energy. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Electrical Power and Energy in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Electrical Power and Energy explains how the physical world behaves, from sport and transport to electricity and medicine.
Electrical Power and Energy in detail
Electrical power is the rate at which energy is transferred: P = VI, which can also be written P = I²R or P = V²/R, measured in watts. Energy transferred is E = Pt, or in terms of charge, E = QV.
Household bills use the kilowatt-hour (kWh), the energy used by a 1 kW device in one hour (3.6 million joules). To calculate cost, multiply the number of kWh by the price per unit. The power rating tells you how fast an appliance uses energy, which helps in choosing fuses and comparing running costs.
How the interactive helps you understand Electrical Power and Energy
Watch the circuit in the interactive. Use any sliders or buttons it offers to change the values and see how the circuit responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Electrical Power and Energy.
Real-life uses and examples
- Answer “explain” questions by linking Electrical Power and Energy to a clear cause and effect.
- Predict what a ball, car or circuit will do with Electrical Power and Energy before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Electrical Power and Energy.
Common mistakes to avoid
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Mixing up Electrical Power and Energy with a related quantity that has different units.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Electrical Power and Energy
What is Electrical Power and Energy?
Electrical power is the rate at which a device transfers energy, equal to the voltage multiplied by the current.
What are the most important points about Electrical Power and Energy?
The main points are: P equals V times I; Energy equals power times time; The kilowatt-hour is the unit on electricity bills.
Why is Electrical Power and Energy useful?
Understanding Electrical Power and Energy explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Electrical Power and Energy?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Electrical Power and Energy?
Related topics in Physics include Magnets and Magnetic Fields, Electromagnetic Induction, The National Grid.