2.3.8

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.
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.
Jump to other topics
1

Forces & Motion

1.1

Basics of Motion

1.1.1Average Speed1.1.2Acceleration1.1.3Distance & Displacement1.1.4Velocity1.1.5Adding Vectors1.1.6Distance-Time Graphs1.1.7Speed-Time Graphs 11.1.8Speed-Time Graphs 21.1.9Initial & Final Speed, Acceleration, Distance1.1.10Average Speed - Calculations1.1.11Acceleration - Calculations1.1.12Uniform Acceleration - Calculations1.1.13Grade 9 - Motion1.1.14Exam-Style Questions - Graphs of Motion
1.2

Forces

1.2.1Contact & Non-Contact Forces1.2.2Examples of Contact Forces1.2.3Friction1.2.4Newton's First Law1.2.5Newton's Second Law1.2.6Newton's Third Law1.2.7Describing Forces1.2.8Using Free Body Diagrams
1.3

Effects of Forces

1.3.1Momentum - No Impulse1.3.2Momentum1.3.3Momentum: Law of Conservation1.3.4Force & Momentum Change1.3.5Momentum - Safety1.3.6Change in Momentum - Calculations1.3.7Momentum - Calculations1.3.8Mass1.3.9Weight1.3.10Centre of Mass1.3.11Gravity - Calculations1.3.12Free Fall1.3.13Air Resistance & Friction1.3.14Graphs of Motion with Air Resistance1.3.15Turning Effect1.3.16Moments1.3.17Equilibrium1.3.18Moments - Calculations1.3.19Exam-Style Questions - Moments
1.4

Stopping Distance

1.4.1Stopping Distance1.4.2Stopping Distance - Thinking Distance1.4.3Stopping Distance - Braking Distance
1.5

Forces & Elasticity

1.5.1Stretching, Bending & Compressing1.5.2Elastic Deformation vs Inelastic Deformation1.5.3Hooke's Law1.5.4Hooke's Law - Equation1.5.5Hooke's Law - Spring Experiments1.5.6Hooke's Law - Calculations1.5.7Elastic Potential - Calculations1.5.8End of Topic Test - Forces1.5.9Exam-Style Questions - Elastic Potential
2

Electricity

2.1

Electricity in Homes

2.1.1Mains Electricity2.1.2Power Rating of Appliances2.1.3National Grid2.1.4AC/DC2.1.5Electrical Safety2.1.6Fuses2.1.7Fuse Ratings
2.2

Current & Potential Difference

2.2.1Current2.2.2Current - Equation2.2.3Current - Calculations2.2.4Conductors & Insulators2.2.5Electrical Conductors - Electrons2.2.6Potential Difference2.2.7Potential Difference - Equation2.2.8Measurements in Circuits2.2.9Voltage - Calculations
2.3

Resistance & Power

2.3.1Resistance2.3.2Ohm's Law2.3.3Measuring Resistance2.3.4Resistance & Ohms Law - Calculations2.3.5Variable Resistance2.3.6Current-Voltage Graph for a Resistor2.3.7Electrical Work2.3.8Power2.3.9Heating Effect in Resistors2.3.10Electrical Work - Calculations2.3.11Exam-Style Questions - Resistance
2.4

Electric Circuits

2.4.1Circuit Diagrams2.4.2Circuit Symbols2.4.3Diodes2.4.4LDRs & Thermistors2.4.5Series Circuits2.4.6Resistors in Series2.4.7Series Circuits - Calculations2.4.8Parallel Circuits2.4.9Parallel Circuits in Practice2.4.10End of Topic Test - Electricity2.4.11Grade 9 - Circuits2.4.12Exam-Style Questions - Electrical Circuits
2.5

Static Electricity

2.5.1Electric Charge2.5.2Charging an Object2.5.3Charged Objects2.5.4Uses of Static Electricity2.5.5Charge Dangers2.5.6Calculating Power & Energy Transferred
3

Waves

3.1

Wave Basics

3.1.1Wave Basics3.1.2Transverse Waves3.1.3Longitudinal Waves3.1.4Wave Frequency Formula3.1.5Wavelength & Amplitude3.1.6Wave Speed3.1.7Wave Speed - Calculations3.1.8Wave Frequency - Calculations3.1.9Wavefronts3.1.10Doppler Effect3.1.11Exam-Style Questions - Wave Speed
3.2

Waves at a Boundary

3.2.1Changing Wave Motion3.2.2Reflection3.2.3Refraction3.2.4Angle of Refraction3.2.5Refractive Index 13.2.6Refractive Index 23.2.7Total Internal Reflection3.2.8Optic Fibres
3.3

Electromagnetic Spectrum

3.3.1Properties of Electromagnetic Waves3.3.2Gamma Rays3.3.3X-Rays3.3.4UV Light3.3.5Visible Light3.3.6Infrared Radiation3.3.7Microwaves3.3.8Radio Waves3.3.9End of Topic Test - EM Waves3.3.10Exam-Style Questions - Electromagnetic Wave Uses
3.4

Sound Waves

3.4.1Sound Waves3.4.2Sound Waves & Our Ears3.4.3Sound as a Wave3.4.4Signal Generators3.4.5Sound Waves - Oscilloscope Traces3.4.6Measuring the Speed of Sound - Experiment3.4.7End of Topic Test - Waves
3.5

Communications

3.5.1Digital & Analogue Signals3.5.2Benefits of Digital Signals
4

Energy Resources & Energy Transfers

4.1

Energy Changes

4.1.1Energy Stores4.1.2Conservation of Energy4.1.3Examples of Energy Conversion4.1.4Kinetic Energy Stored4.1.5Gravitational Potential Energy Stored4.1.6Elastic Potential Energy Stored4.1.7Changes in Kinetic Energy - Calculations4.1.8Changes in GPE - Calculations4.1.9Changes in EPE - Calculations4.1.10Mechanical Work Done4.1.11Mechanical Work Done - Equation4.1.12Power4.1.13Mechanical Work - Calculations4.1.14Electrical Work Done- Calculations
4.2

Energy Losses & Efficiency

4.2.1Energy Wastage4.2.2Energy Transfer Diagrams4.2.3Efficiency4.2.4Reducing Unwanted Energy Transfer4.2.5Efficiency - Calculations4.2.6Grade 9 - Energy & Efficiency4.2.7Exam-Style Questions - Energy & Power
4.3

Energy Resources

4.3.1Energy Resources4.3.2Fossil Fuels4.3.3Geothermal Energy4.3.4Wind Energy4.3.5Water Energy4.3.6Tidal Energy4.3.7Nuclear Energy4.3.8Solar Energy4.3.9Non-Renewable & Renewable Resources4.3.10Renewable Energy4.3.11Limits to Renewable Energy Resources4.3.12End of Topic Test - Energy
4.4

Thermal Processes

4.4.1Radiation4.4.2Conduction4.4.3Molecular Conduction4.4.4Convection Currents4.4.5Convection Currents - Examples
5

Solids, Liquids & Gases

5.1

Density & Pressure

5.1.1Density5.1.2Density Equation5.1.3Calculating Density5.1.4Density - Calculations5.1.5Pressure5.1.6Atmospheric Pressure5.1.7Pressure Difference5.1.8Pressure - Calculations
5.2

Changing State

5.2.1Changes of State5.2.2States of Matter5.2.3Specific Heat Capacity5.2.4Exam-Style Questions - Specific Heat5.2.5Internal Energy - Calculations
5.3

Ideal Gases

5.3.1Kelvin Scale & Absolute Zero5.3.2Temperature & the Kelvin Scale5.3.3Properties of Gases5.3.4Temperature Increase in a Gas5.3.5End of Topic Test - Solids, Liquids & Gases5.3.6Grade 9 - Solids, Liquids & Gases
6

Magnetism & Electromagnetism

6.1

Magnetism

6.1.1Magnetism6.1.2Magnetic Materials6.1.3Hard & Soft Magnets6.1.4Induced Magnetism6.1.5Magnetic Forces6.1.6Magnetic Field Patterns6.1.7Exam-Style Questions - Magnetic Fields
6.2

Electromagnetism

6.2.1The Magnetic Effect of a Current6.2.2Magnetic Field around a Coil of Wire6.2.3Magnetic Field Strength6.2.4The Motor Effect6.2.5Direction of the Motor Effect6.2.6The Catapult Experiment6.2.7Force on a Current Carrying Wire6.2.8DC Motors6.2.9Loudspeakers
6.3

Electromagnetic Induction

6.3.1Electromagnetic Induction6.3.2Induced Potential Difference6.3.3Alternating Current - The Rotating-Coil Generator
6.4

Transformers

6.4.1Transformers6.4.2Transformer Equation6.4.3Step-Up & Step-Down Transformers6.4.4Principles of Transformer Operation6.4.5High-Voltage Transmission & Transformers6.4.6Transformers - Calculations6.4.7Transformers 2 - Calculations6.4.8Energy in Transformers6.4.9Power Losses in Cables6.4.10End of Topic Test - Magnetism6.4.11Grade 9 - Transformers6.4.12Exam-Style Questions - Transformers
7

Radioactivity & Particles

7.1

Atoms

7.1.1Atomic Model7.1.2Structure of an Atom7.1.3The Charges of Sub-Atomic Particles7.1.4Alpha Particles7.1.5The Model of the Atom7.1.6Proton & Nucleon Numbers7.1.7Atoms & Ions7.1.8Isotopes 17.1.9Isotopes 27.1.10Carbon Nuclides
7.2

Radioactivity

7.2.1Radioactive Decay7.2.2Types of Radiation7.2.3Three Types of Emission7.2.4Ionising vs Penetration7.2.5Nuclear Fission7.2.6Nuclear Reactors7.2.7Nuclear Fission - Uncontrolled Chain Reaction7.2.8Radioactive Decay7.2.9Decay Equations7.2.10Nuclear Fission Equation7.2.11Half Life & Background Radiation7.2.12Measuring Half-Life From a Graph7.2.13Background Radiation7.2.14Practical Applications of Radiation7.2.15Ions & Ionising Radiation7.2.16Safety Precautions7.2.17Peer Review7.2.18End of Topic Test - Radioactivity & Particles7.2.19Grade 9 - Radioactivity & Particles7.2.20Exam-Style Questions - Radioactive Decay
8

Astrophysics

8.1

Motion in the Universe

8.1.1The Solar System8.1.2Gravitational Field Strength8.1.3Orbits8.1.4Orbital Motion
8.2

Evolution of Stars

8.2.1Life Cycle of a Star like the Sun8.2.2Life Cycle of a Star Much Bigger than the Sun8.2.3Absolute Magnitude8.2.4Hertzsprung-Russell Diagrams8.2.5Exam-Style Questions - Life Cycle of a Star
8.3

Cosmology

8.3.1The Big Bang8.3.2Evidence for the Big Bang8.3.3CMB Radiation8.3.4End of Topic Test - 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

Heating Effect in Resistors