2.2.7

Power

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Power

Power (P) is the rate of energy transfer to a component.

Power

Power

  • The power of a component is equal to the current through the component multiplied by the potential difference across the component.
  • P = I x V.
  • We know V = IR, so power can also be calculated by:
    • P = I2R
Total energy transfer

Total energy transfer

  • The total energy transferred to a component is equal to the power multiplied by the time a current flows for.
  • E = P x t.
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1

Energy

1.1

Energy Changes

1.1.1Energy Stores1.1.2Energy Storing1.1.3Internal Energy1.1.4Kinetic Energy Storage1.1.5Gravitational Potential Energy Storage1.1.6Elastic Potential Energy Storage1.1.7Calculating Changes in Energy1.1.8Changes in Kinetic Energy - Calculations1.1.9Changes in GPE - Calculations1.1.10Changes in EPE - Calculations1.1.11Energy Transfers1.1.12Energy Transfer Examples1.1.13Conservation of Energy1.1.14Mechanical Work - Calculations1.1.15Mechanical Work Done1.1.16Mechanical Work Done Equation1.1.17Electrical Work Done1.1.18Power1.1.19Electrical Work Done- Calculations1.1.20Diagnostic Misconceptions - Stationary Objects
1.2

Energy Losses & Efficiency

1.2.1Energy Wastage1.2.2Energy Efficiency1.2.3Reducing Energy Loss1.2.4Power & Energy Transfer1.2.5Required Practical - Investigating Insulation1.2.6Efficiency - Calculations1.2.7Grade 9 - Energy & Efficiency
1.3

Energy Resources

1.3.1Energy Resources1.3.2Fossil Fuels1.3.3Geothermal Energy1.3.4Wind Energy1.3.5Water Energy1.3.6Tidal Energy1.3.7Nuclear Energy1.3.8Solar Energy1.3.9Original Source of Energy1.3.10Non-Renewable & Renewable Resources1.3.11Uses of Energy Sources1.3.12Changing Electricity Use1.3.13Renewable Energy1.3.14Limits to Renewable Energy Resources1.3.15End of Topic Test - Energy1.3.16Exam-Style Questions - Energy
2

Electricity

2.1

Electric Charge

2.1.1Circuit Diagrams2.1.2Circuit Symbols2.1.3Current2.1.4Current Equation2.1.5Current - Calculations2.1.6Conductors2.1.7Electrical Conductors - Electrons2.1.8Potential Difference2.1.9Voltage Equation2.1.10Measurements in Circuit2.1.11Voltage - Calculations2.1.12Diagnostic Misconceptions - Powering a Circuit
2.2

Resistance & Electrical Work

2.2.1Resistance2.2.2Measuring Resistance2.2.3Resistance Graph2.2.4Diodes2.2.5LDRs & Thermistors2.2.6Electrical Work2.2.7Power2.2.8Ohm's Law2.2.9Ohm's Law - Equation2.2.10Resistance & Ohms Law - Calculations2.2.11Electrical Work - Calculations2.2.12Required Practical - Investigating Resistance
2.3

Electric Circuits

2.3.1Series Circuits2.3.2Resistors2.3.3Required Practical - I–V Characteristics2.3.4Cells in Series2.3.5Series Circuits - Calculations2.3.6Parallel Circuits2.3.7Parallel Current2.3.8Parallel Resistance2.3.9Lights in Parallel2.3.10Parallel Circuits - Calculations2.3.11Grade 9 - Circuits2.3.12Exam-Style Questions - Electricity
2.4

Electricity in Homes

2.4.1AC/DC2.4.2Mains Electricity2.4.3Power Ratings2.4.4National Grid2.4.5Domestic Uses - Calculations2.4.6Fuses & Circuit Breakers2.4.7Fuse Ratings2.4.8Earthing2.4.9Dangers of the Live Wire2.4.10End of Topic Test - Electricity
2.5

Static Electricity

2.5.1Electrical Charge2.5.2Charging an Object2.5.3Charged Objects2.5.4Static Electricity2.5.5Electric Fields2.5.6Field Diagrams
3

Particle Model of Matter

3.1

States of Matter

3.1.1Atomic Model3.1.2Atomic Structure3.1.3Sub-Atomic Particles3.1.4Models of the Atom3.1.5Alpha Particles3.1.6Electron Arrangements3.1.7Density3.1.8Density Equation3.1.9Density & the Particle Model3.1.10Density - Calculations3.1.11Changes of State3.1.12Melting & Boiling3.1.13Exam-Style Questions - Density3.1.14Required Practical - Density3.1.15Diagnostic Misconceptions - Floating3.1.16Diagnostic Misconceptions - Volume
3.2

Heat

3.2.1Internal Energy3.2.2Change in Thermal Energy3.2.3Required Practical - Specific Heat Capacity3.2.4Equation for Heat Capacity3.2.5Leslie's Cube3.2.6Internal Energy - Calculations3.2.7Melting & Boiling3.2.8Latent Heat3.2.9Energy Change for Change of State3.2.10Latent Heat - Calculations3.2.11Specific Latent Heat of Fusion3.2.12Specific Latent Heat of Vaporisation
3.3

Particle Motion in Gases

3.3.1States of Matter3.3.2Properties of Gases3.3.3Temperature Increase in a Gas3.3.4Work Done on a Gas3.3.5End of Topic Test - Particle Model of Matter3.3.6Grade 9 - Particle Model of Matter3.3.7Exam-Style Questions - Specific Heat Capacity
4

Atoms & Radiation

4.1

Atoms

4.1.1Atomic Model4.1.2Structure of an Atom4.1.3Sub-Atomic Particles4.1.4Alpha Particles4.1.5The Model of the Atom4.1.6Electron Arrangements4.1.7Proton & Nucleon Numbers4.1.8Atoms & Ions4.1.9Isotopes 14.1.10Isotopes 24.1.11Carbon Nuclides4.1.12Exam-Style Questions - Atomic Structure4.1.13Diagnostic Misconceptions - Types of Radiation
4.2

Radiation

4.2.1Radioactivity4.2.2Types of Radiation4.2.3Detection of Radiation4.2.4Background Radiation4.2.5Types of Radioactive Emission4.2.6Ionising vs Penetration4.2.7Practical Applications of Radiation4.2.8Nuclear Fission4.2.9Nuclear Fission 24.2.10Nuclear Fusion4.2.11Radioactive Decay4.2.12Radioactive Decay Equations4.2.13Radioactive Decay Equations - Calculations4.2.14Radioactive Decay4.2.15Fission & Fusion Equations4.2.16Half Lives4.2.17Measuring Half Lives4.2.18Ionising Radiation4.2.19Half Life - Calculations4.2.20Safety Precautions4.2.21Uses for Isotopes With Different Half-lives4.2.22Radioactive Contamination & Irradiation4.2.23Types of Contamination4.2.24Required Practical - Radiation4.2.25Peer Review4.2.26End of Topic Test - Atoms & Radiation4.2.27Grade 9 - Radiation4.2.28Exam-Style Questions - Radioactive Decay
5

Forces

5.1

Basics of Motion

5.1.1Velocity5.1.2Average Speed5.1.3Adding Vectors5.1.4Acceleration5.1.5Distance vs Displacement5.1.6Contact & Non-Contact Forces5.1.7Contact Forces - Examples5.1.8Distance-Time Graphs5.1.9Speed-Time Graphs5.1.10Velocity - Time Graph5.1.11Average Speed - Calculations5.1.12Acceleration - Calculations5.1.13Uniform Acceleration - Calculations5.1.14Grade 9 - Motion5.1.15Exam-Style Questions - Motion5.1.16Diagnostic Misconception - Motion5.1.17Diagnostic Misconceptions - Acceleration
5.2

Forces

5.2.1Mass & Inertia5.2.2Weight5.2.3Centre of Mass5.2.4Gravity - Calculations5.2.5Resultant Forces5.2.6Newton's First Law5.2.7Newton Second Law - Calculations5.2.8Newton's Third Law5.2.9Free Body Force Diagrams5.2.10Free Body Diagram - Uses5.2.11Components of Forces5.2.12Free Body Diagrams - Calculations5.2.13Stretching a Spring5.2.14Elastic vs Inelastic Deformation5.2.15Hooke's Law & Equation5.2.16Hooke's Law - Equation5.2.17Hooke's Law - Calculations5.2.18Required Practical - Spring5.2.19Elastic Potential Energy5.2.20Elastic Potential Energy - Equation5.2.21Elastic Potential - Calculations5.2.22Exam-Style Questions - Elastic Potential Energy5.2.23Diagnostic Misconceptions - Weight & Mass
5.3

Effects of Forces

5.3.1Free Fall5.3.2Free Fall - Graphs5.3.3Air Resistance & Friction5.3.4Graphing Acceleration5.3.5Required Practical - Effects on Acceleration5.3.6Motion with Air Resistance5.3.7Momentum5.3.8Momentum: Law of Conservation5.3.9Force & Momentum Change5.3.10Momentum - Equation5.3.11Change in Momentum - Calculations5.3.12Momentum - Calculations5.3.13Turning Effect5.3.14Moments5.3.15Equilibrium5.3.16Moments - Calculations5.3.17Circular Motion5.3.18Levers & Gears5.3.19Gears5.3.20Stopping Distance5.3.21Factors Affecting Stopping Distance5.3.22Factors Affecting Braking Distance5.3.23Decelerations5.3.24Dangers of Large Decelerations5.3.25Stopping Distance - Calculations5.3.26Diagnostic Misconceptions - Upward Moving Objects
5.4

Pressure

5.4.1Pressure & Force on Container5.4.2Atmospheric Pressure5.4.3Liquid Pressure5.4.4Pressure - Calculations5.4.5Liquid Pressure - Calculations5.4.6Upthrust5.4.7Depth Control of Submarine5.4.8Pressure Difference5.4.9End of Topic Test - Forces5.4.10Exam-Style Questions - Pressure
6

Waves

6.1

Wave Basics

6.1.1Wave Basics6.1.2Wave Speed Formula6.1.3Wave Speed Equation6.1.4Wave Speed - Calculations6.1.5Wave Frequency Formula6.1.6Wavelength & Amplitude6.1.7Wave Frequency - Calculations6.1.8Transverse Waves6.1.9Longitudinal Wave6.1.10Required Practical - Ripple Tank6.1.11Diagnostic Misconceptions - Wavelength
6.2

Waves at a Boundary

6.2.1Waves at a Boundary6.2.2Waves at a Boundary 26.2.3Reflection of Light6.2.4Refraction of Light6.2.5Refraction of Light 26.2.6Internal Reflection6.2.7Required Practical - Reflection and Refraction
6.3

Sound Waves

6.3.1Sound Waves6.3.2Sound Waves & our Ears6.3.3Speed of Sound 16.3.4Speed of Sound 26.3.5Sound as a Wave6.3.6Uses of Sound Waves: Ultrasound Waves6.3.7Uses of Sound Waves: Earthquakes6.3.8Sound Waves - Calculations6.3.9End of Topic Test - Introduction to Waves6.3.10Exam-Style Questions - Wave Speed
6.4

Electromagnetic Waves

6.4.1Properties of Electromagnetic Waves6.4.2Gamma Rays6.4.3X-Rays6.4.4UV Light6.4.5Infrared Radiation6.4.6Microwaves6.4.7Radio Waves6.4.8Properties 26.4.9Visible Light6.4.10Visible Light 26.4.11Specular & Diffuse Reflection6.4.12Colours6.4.13Grade 9 - Waves
6.5

Lenses

6.5.1Lenses6.5.2Convex Lens6.5.3Concave Lens6.5.4Lenses - Calculations6.5.5Images6.5.6Ray Diagrams6.5.7Ray Diagrams 2
6.6

Heat & Radiation

6.6.1Infrared Radiation6.6.2Radiation & Surface Colour6.6.3Surface Area & Temperature6.6.4Temperature6.6.5Absorption & Emission6.6.6Greenhouse Effect6.6.7Energy Balance of the Earth6.6.8End of Topic Test - EM Waves, Lenses & Heat6.6.9Exam-Style Questions - EM Radiation
7

Magnetism

7.1

Magnetism Basics

7.1.1Magnetism7.1.2Magnetic Materials7.1.3Induced Magnetism7.1.4Magnetic Fields7.1.5Magnetic Field Patterns
7.2

Electromagnetism

7.2.1The Magnetic Effect of a Current7.2.2Solenoid Field7.2.3Magnetic Field Strength7.2.4Uses of Electromagnets7.2.5Motor Effect7.2.6Direction of Motor Effect7.2.7Magnetic Flux Equation7.2.8Magnetic Flux - Calculations7.2.9Electric Motors7.2.10Loudspeakers7.2.11Force Acting on a Coil in a Magnetic Field7.2.12Induced Potential Difference7.2.13Increasing the Induced Potential Difference7.2.14Magnetic Field Direction7.2.15Forces Between Electricity & Magnets7.2.16AC/DC7.2.17AC Generators7.2.18Generator Effect7.2.19Microphones
7.3

Transformers

7.3.1Transformers7.3.2Transformer Equation7.3.3Step-Up & Step-Down Transformers7.3.4Principles of Transformer Operation7.3.5High-Voltage Transmission & Transformers7.3.6Energy in Transformers7.3.7Power Losses in Cables7.3.8Transformers - Calculations7.3.9Transformers 2 - Calculations7.3.10End of Topic Test - Magnetism7.3.11Grade 9 - Transformers7.3.12Exam-Style Questions - Magnetic Fields
8

Astrophysics

8.1

Astrophysics

8.1.1The Solar System8.1.2The Sun8.1.3The Solar System - Calculations8.1.4Orbits8.1.5Stable Orbits8.1.6Orbits HyperLearning8.1.7Life Cycle of a Star like the Sun8.1.8Life Cycle of a Star Much Bigger than the Sun8.1.9Creation of Elements8.1.10Red-shift8.1.11The Big Bang Theory8.1.12Gaps in Knowledge8.1.13End of Topic Test - Astrophysics8.1.14Exam-Style Questions - Astrophysics

Practice questions on Power

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    When a current flows through a light bulb, it emits 30 J light energy in 2 seconds, what is the power of the bulb?Multiple choice
  2. 2
    When the potential difference across a component and the resistance are known, which formula can be used to calculate power?Multiple choice
  3. 3
    What does the term "rate of energy transfer" refer to, in the context of power in electric circuits?Multiple choice
  4. 4
    How does an increase in resistance affect the power dissipated in a component when the current remains constant?Multiple choice
  5. 5
    In the formula P = I²R, what is the significance of I²?Multiple choice
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Electrical Work

Ohm's Law