Ever wondered how much energy your phone charger actually uses,...
Physics73 views·Updated 18 Aug 2026·2 pagesN5 Physics: Understanding Power, Current, and Voltage
1
of 2
Power Relationships
Your everyday electrical devices all have one thing in common - they convert electrical energy into other forms like light, heat, or sound. Power tells us how quickly this energy conversion happens, and it's directly linked to current and voltage.
The fundamental relationship is P = IV, where P is power (measured in watts), I is current (amperes), and V is voltage (volts). Think of it this way: more current or higher voltage means more power being used.
There's another useful form: P = I²R. This comes from substituting V = IR into our original equation. This relationship is particularly handy when you know the current and resistance but not the voltage directly.
Quick Check: A 3A current flowing through a 4Ω resistor uses P = 3² × 4 = 36W of power.
2
of 2
Power Calculations Made Simple
The third power equation, P = V²/R, is brilliant for situations where you know voltage and resistance. It comes from rearranging Ohm's law and substituting into P = IV.
These three equations give you flexibility in calculations - you can find power using any two of the three electrical quantities (voltage, current, resistance). Choose whichever equation fits the information you're given.
Here's your complete toolkit: P = E/t (energy per time), P = IV (voltage-current), P = I²R (current-resistance), and P = V²/R (voltage-resistance). Master these, and you'll breeze through any power calculation.
Exam Tip: Always check your units! Power should come out in watts (W), and remember that 1000W = 1kW.
We thought you’d never ask...
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar content
Most popular content: Voltage
6PhysicsPhysics Paper 1 Overview
Comprehensive summary of AQA Physics Paper 1, covering key concepts such as radioactivity, energy sources, atomic structure, and electrical circuits. Ideal for exam preparation, this resource includes essential topics like half-life, nuclear fission and fusion, and the National Grid. Enhance your understanding of physics with this detailed guide.
111,02119
PhysicsKey Physics Experiments
Explore essential GCSE physics experiments covering density, resistance, wave phenomena, and Hooke's Law. This practical guide includes step-by-step procedures for measuring specific heat capacity, analyzing series and parallel circuits, and understanding motion mechanics. Ideal for students preparing for exams.
111814
PhysicsElectricity Circuit Fundamentals
Explore the essential concepts of electricity and circuits, including Ohm's Law, resistance in series and parallel circuits, and power formulas. This summary covers key topics such as current, voltage, and circuit symbols, providing a comprehensive overview for physics students. Ideal for exam preparation and quick revision.
73473
PhysicsElectricity Fundamentals Overview
Explore key concepts in electricity with this comprehensive booklet designed for AQA Physics. Covering topics such as static electricity, current, voltage, and energy efficiency, this resource includes past paper questions and mark schemes to help identify and strengthen your understanding of electricity in the home and beyond. Ideal for exam preparation and revision.
111,42339
PhysicsUnderstanding Electrical Circuits
Explore the fundamentals of electricity, including Ohm's Law, series and parallel circuits, and the components of household electrical systems. This summary covers key concepts such as electric current, resistance, power, and energy transfer, essential for Edexcel GCSE Physics. Ideal for students preparing for exams.
1175719
PhysicsElectricity Fundamentals Overview
Explore key concepts in electricity, including current, voltage, resistance, and circuit types. This summary covers Ohm's Law, power calculations, and the behavior of resistors in series and parallel circuits. Ideal for Physics P2 revision, this resource provides essential insights for understanding electrical systems and their components.
11921
Most popular content in Physics
6PhysicsForces and Motion Overview
Explore key concepts in Forces and Motion, including Hooke's Law, velocity, acceleration, and the principles of moments. This summary covers essential topics such as the relationship between force and extension, terminal velocity, and the impact of safety devices in physics. Ideal for AQA Physics Unit 5 revision.
109,249872
PhysicsPhysics paper 2 notes
physics aqa gcse paper 2 combined higher notes
111,25810
PhysicsPhysics Paper 2 Essentials
Master key concepts for AQA Combined Physics Paper 2, including electromagnetic waves, mechanics, forces, and motion. This comprehensive summary covers essential topics like wave properties, Newton's laws, and the motor effect, ensuring you're well-prepared for your exam.
1116,081941
PhysicsGCSE Physics Practical Experiments
Explore essential GCSE Physics practicals for AQA, covering key concepts such as Hooke's Law, wave properties, thermal insulation, and electrical circuits. This comprehensive guide includes step-by-step procedures, variables, and safety considerations for each experiment, ensuring a thorough understanding of practical applications in physics.
1011,423477
Physicsphysics paper 2 foundation notes
aqa combined science physics paper 2 foundation notes
111,33438
PhysicsPhysics Paper 1 Edexcel Notes (Topic 1-7)
Edexcel GCSE Physics full specification notes topics: SP1 Key Concepts in Physics, SP2 Motion and Forces, SP3 Conservation of Energy, SP4 Waves, SP5 Light and Electromagnetic Spectrum, SP6 Radioactivity, SP7 Astronomy. Useful for making flashcards!
112,04027
Most popular content
6
SociologyComprehensive Crime & Deviance Overview
Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.
1251,7101,402
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1273,8942,306
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1254,9161,061
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
127,186125
SociologyMedia Studies: Key Concepts & Theories
Dive into the essential concepts and theories of media studies for AQA A-level Sociology. This comprehensive revision guide covers topics such as media influence, representations, globalization, and sociological perspectives, ensuring you grasp the critical elements needed for your exams. Perfect for students seeking to enhance their understanding of media's role in society.
1222,755515
SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12103,0623,042
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user
Physics73 views·Updated 18 Aug 2026·2 pagesN5 Physics: Understanding Power, Current, and Voltage
Ever wondered how much energy your phone charger actually uses, or why some devices get hot when they're working? Power relationshipsin electricity help us understand how electrical energy flows and gets converted in circuits - knowledge that's essential for...
1
of 2
Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Power Relationships
Your everyday electrical devices all have one thing in common - they convert electrical energy into other forms like light, heat, or sound. Power tells us how quickly this energy conversion happens, and it's directly linked to current and voltage.
The fundamental relationship is P = IV, where P is power (measured in watts), I is current (amperes), and V is voltage (volts). Think of it this way: more current or higher voltage means more power being used.
There's another useful form: P = I²R. This comes from substituting V = IR into our original equation. This relationship is particularly handy when you know the current and resistance but not the voltage directly.
Quick Check: A 3A current flowing through a 4Ω resistor uses P = 3² × 4 = 36W of power.
2
of 2Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Power Calculations Made Simple
The third power equation, P = V²/R, is brilliant for situations where you know voltage and resistance. It comes from rearranging Ohm's law and substituting into P = IV.
These three equations give you flexibility in calculations - you can find power using any two of the three electrical quantities (voltage, current, resistance). Choose whichever equation fits the information you're given.
Here's your complete toolkit: P = E/t (energy per time), P = IV (voltage-current), P = I²R (current-resistance), and P = V²/R (voltage-resistance). Master these, and you'll breeze through any power calculation.
Exam Tip: Always check your units! Power should come out in watts (W), and remember that 1000W = 1kW.
We thought you’d never ask...
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar content
Most popular content: Voltage
6PhysicsPhysics Paper 1 Overview
Comprehensive summary of AQA Physics Paper 1, covering key concepts such as radioactivity, energy sources, atomic structure, and electrical circuits. Ideal for exam preparation, this resource includes essential topics like half-life, nuclear fission and fusion, and the National Grid. Enhance your understanding of physics with this detailed guide.
111,02119
PhysicsKey Physics Experiments
Explore essential GCSE physics experiments covering density, resistance, wave phenomena, and Hooke's Law. This practical guide includes step-by-step procedures for measuring specific heat capacity, analyzing series and parallel circuits, and understanding motion mechanics. Ideal for students preparing for exams.
111814
PhysicsElectricity Circuit Fundamentals
Explore the essential concepts of electricity and circuits, including Ohm's Law, resistance in series and parallel circuits, and power formulas. This summary covers key topics such as current, voltage, and circuit symbols, providing a comprehensive overview for physics students. Ideal for exam preparation and quick revision.
73473
PhysicsElectricity Fundamentals Overview
Explore key concepts in electricity with this comprehensive booklet designed for AQA Physics. Covering topics such as static electricity, current, voltage, and energy efficiency, this resource includes past paper questions and mark schemes to help identify and strengthen your understanding of electricity in the home and beyond. Ideal for exam preparation and revision.
111,42339
PhysicsUnderstanding Electrical Circuits
Explore the fundamentals of electricity, including Ohm's Law, series and parallel circuits, and the components of household electrical systems. This summary covers key concepts such as electric current, resistance, power, and energy transfer, essential for Edexcel GCSE Physics. Ideal for students preparing for exams.
1175719
PhysicsElectricity Fundamentals Overview
Explore key concepts in electricity, including current, voltage, resistance, and circuit types. This summary covers Ohm's Law, power calculations, and the behavior of resistors in series and parallel circuits. Ideal for Physics P2 revision, this resource provides essential insights for understanding electrical systems and their components.
11921
Most popular content in Physics
6PhysicsForces and Motion Overview
Explore key concepts in Forces and Motion, including Hooke's Law, velocity, acceleration, and the principles of moments. This summary covers essential topics such as the relationship between force and extension, terminal velocity, and the impact of safety devices in physics. Ideal for AQA Physics Unit 5 revision.
109,249872
PhysicsPhysics paper 2 notes
physics aqa gcse paper 2 combined higher notes
111,25810
PhysicsPhysics Paper 2 Essentials
Master key concepts for AQA Combined Physics Paper 2, including electromagnetic waves, mechanics, forces, and motion. This comprehensive summary covers essential topics like wave properties, Newton's laws, and the motor effect, ensuring you're well-prepared for your exam.
1116,081941
PhysicsGCSE Physics Practical Experiments
Explore essential GCSE Physics practicals for AQA, covering key concepts such as Hooke's Law, wave properties, thermal insulation, and electrical circuits. This comprehensive guide includes step-by-step procedures, variables, and safety considerations for each experiment, ensuring a thorough understanding of practical applications in physics.
1011,423477
Physicsphysics paper 2 foundation notes
aqa combined science physics paper 2 foundation notes
111,33438
PhysicsPhysics Paper 1 Edexcel Notes (Topic 1-7)
Edexcel GCSE Physics full specification notes topics: SP1 Key Concepts in Physics, SP2 Motion and Forces, SP3 Conservation of Energy, SP4 Waves, SP5 Light and Electromagnetic Spectrum, SP6 Radioactivity, SP7 Astronomy. Useful for making flashcards!
112,04027
Most popular content
6SociologyComprehensive Crime & Deviance Overview
Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.
1251,7101,402
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1273,8942,306
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1254,9161,061
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
127,186125
SociologyMedia Studies: Key Concepts & Theories
Dive into the essential concepts and theories of media studies for AQA A-level Sociology. This comprehensive revision guide covers topics such as media influence, representations, globalization, and sociological perspectives, ensuring you grasp the critical elements needed for your exams. Perfect for students seeking to enhance their understanding of media's role in society.
1222,755515
SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12103,0623,042
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user