Conservation of Energy

The principle of the conservation of energy says that energy cannot be created or destroyed. Energy can only be transformed from one store of energy into another. There are four ways that energy can be transformed:

Mechanical work

Energy transferred from one object to another via a force is an example of mechanical work.
- When an object falls from a building, the weight does mechanical work to transfer energy from the gravitational potential store to the kinetic store.
- When you push a wheelchair, energy is transferred to the kinetic store of the wheelchair.

Electrical work

An electrical current transfers energy from one object to another, such as a battery powering a torch.

Heating

Heating an object transfers energy to the object's internal store of energy.
The internal energy is the sum of the energy in the kinetic and chemical stores of an object's particles.

Waves

Light and other types of waves can transfer energy from one object to another.

E.g. - An object hitting an obstacle

The object's energy is in the kinetic store at the start because it is moving.
When the object collides with the obstacle, energy is converted to:
- The kinetic store of the obstacle (making it move).
- The thermal store of the object and the obstacle (the particles in the object and the obstacle vibrate more).
Some energy remains in the object's kinetic store as it moves away after the collision.

1Energy

1.1Energy Changes

1.1.1Energy Stores

1.1.2Energy Storing

1.1.3Internal Energy

1.1.4Kinetic Energy Storage

1.1.5Gravitational Potential Energy Storage

1.1.6Elastic Potential Energy Storage

1.1.7Calculating Changes in Energy

1.1.8Changes in Kinetic Energy - Calculations

1.1.9Changes in GPE - Calculations

1.1.10Changes in EPE - Calculations

1.1.11Energy Transfers

1.1.12Energy Transfer Examples

1.1.13Conservation of Energy

1.1.14Mechanical Work Done

1.1.15Mechanical Work Done Equation

1.1.16Mechanical Work - Calculations

1.1.17Electrical Work Done

1.1.18Power

1.1.19Electrical Work Done- Calculations

1.2Energy Losses & Efficiency

1.2.1Energy Wastage

1.2.2Energy Efficiency

1.2.3Reducing Energy Loss

1.2.4Power & Energy Transfer

1.2.5Efficiency - Calculations

1.2.6Grade 9 - Energy & Efficiency

1.3Energy Resources

1.3.1Energy Resources

1.3.2Fossil Fuels

1.3.3Geothermal Energy

1.3.4Wind Energy

1.3.5Water Energy

1.3.6Tidal Energy

1.3.7Nuclear Energy

1.3.8Solar Energy

1.3.9Original Source of Energy

1.3.10Non-Renewable & Renewable Resources

1.3.11Uses of Energy Sources

1.3.12Changing Electricity Use

1.3.13Renewable Energy

1.3.14Limits to Renewable Energy Resources

1.3.15End of Topic Test - Energy

1.3.16Exam-Style Questions - Energy

2Electricity

2.1Electric Charge

2.1.1Circuit Diagrams

2.1.2Circuit Symbols

2.1.3Current

2.1.4Current Equation

2.1.5Current - Calculations

2.1.6Conductors

2.1.7Electrical Conductors - Electrons

2.1.8Potential Difference

2.1.9Voltage Equation

2.1.10Measurements in Circuit

2.1.11Voltage - Calculations

2.2Resistance & Electrical Work

2.2.1Resistance

2.2.2Measuring Resistance

2.2.3Resistance Graph

2.2.4Diodes

2.2.5LDRs & Thermistors

2.2.6Electrical Work

2.2.7Power

2.2.8Ohm's Law

2.2.9Ohm's Law - Equation

2.2.10Resistance & Ohms Law - Calculations

2.2.11Electrical Work - Calculations

2.3Electric Circuits

2.3.1Series Circuits

2.3.2Resistors

2.3.3Cells

2.3.4Potential Difference

2.3.5Series Circuits - Calculations

2.3.6Parallel Circuits

2.3.7Parallel Current

2.3.8Parallel Resistance

2.3.9Lights in Parallel

2.3.10Parallel Circuits - Calculations

2.3.11Grade 9 - Circuits

2.3.12Exam-Style Questions - Electricity

2.4Electricity in Homes

2.4.1AC/DC

2.4.2Mains Electricity

2.4.3Power Ratings

2.4.4National Grid

2.4.5Domestic Uses - Calculations

2.4.6Fuses & Circuit Breakers

2.4.7Fuse Ratings

2.4.8Earthing

2.4.9Dangers of the Live Wire

2.4.10End of Topic Test - Electricity

2.5Static Electricity

2.5.1Electrical Charge

2.5.2Charging an Object

2.5.3Charged Objects

2.5.4Static Electricity

2.5.5Electric Fields

2.5.6Field Diagrams

3Particle Model of Matter

3.1States of Matter

3.1.1Atomic Model

3.1.2Atomic Structure

3.1.3Sub-Atomic Particles

3.1.4Models of the Atom

3.1.5Alpha Particles

3.1.6Electron Arrangements

3.1.7Density

3.1.8Density Equation

3.1.9Density & the Particle Model

3.1.10Density - Calculations

3.1.11Changes of State

3.1.12Melting & Boiling

3.1.13Exam-Style Questions - Density

3.2Heat

3.2.1Internal Energy

3.2.2Change in Thermal Energy

3.2.3Specific Heat Capacity Experiment

3.2.4Equation for Heat Capacity

3.2.5Leslie's Cube

3.2.6Internal Energy - Calculations

3.2.7Melting & Boiling

3.2.8Latent Heat

3.2.9Energy Change for Change of State

3.2.10Latent Heat - Calculations

3.2.11Latent Heat Experiments

3.2.12Specific Latent Heat of Vapourisation

3.3Particle Motion in Gases

3.3.1States of Matter

3.3.2Properties of Gases

3.3.3Temperature Increase in a Gas

3.3.4Work Done on a Gas

3.3.5End of Topic Test - Particle Model of Matter

3.3.6Grade 9 - Particle Model of Matter

3.3.7Exam-Style Questions - Specific Heat Capacity

4Atoms & Radiation

4.1Atoms

4.1.1Atomic Model

4.1.2Structure of an Atom

4.1.3Sub-Atomic Particles

4.1.4Alpha Particles

4.1.5The Model of the Atom

4.1.6Electron Arrangements

4.1.7Proton & Nucleon Numbers

4.1.8Atoms & Ions

4.1.9Isotopes 1

4.1.10Isotopes 2

4.1.11Carbon Nuclides

4.1.12Exam-Style Questions - Atomic Structure

4.2Radiation

5Forces

5.1Basics of Motion

5.1.1Velocity

5.1.2Average Speed

5.1.3Adding Vectors

5.1.4Acceleration

5.1.5Distance vs Displacement

5.1.6Contact & Non-Contact Forces

5.1.7Contact Forces - Examples

5.1.8Distance-Time Graphs

5.1.9Speed-Time Graphs

5.1.10Velocity - Time Graph

5.1.11Average Speed - Calculations

5.1.12Acceleration - Calculations

5.1.13Uniform Acceleration - Calculations

5.1.14Grade 9 - Motion

5.1.15Exam-Style Questions - Motion

5.2Forces

5.3Effects of Forces

5.4Pressure

5.4.1Pressure & Force on Container

5.4.2Atmospheric Pressure

5.4.3Liquid Pressure

5.4.4Pressure - Calculations

5.4.5Liquid Pressure - Calculations

5.4.6Upthrust

5.4.7Depth Control of Submarine

5.4.8Pressure Difference

5.4.9End of Topic Test - Forces

5.4.10Exam-Style Questions - Pressure

6Waves

6.1Wave Basics

6.1.1Wave Basics

6.1.2Wave Speed Formula

6.1.3Wave Speed Equation

6.1.4Wave Speed - Calculations

6.1.5Wave Frequency Formula

6.1.6Wavelength & Amplitude

6.1.7Wave Frequency - Calculations

6.1.8Transverse Waves

6.1.9Longitudinal Wave

6.1.10Required Practical - Ripple Tank

6.2Waves at a Boundary

6.2.1Waves at a Boundary

6.2.2Waves at a Boundary 2

6.2.3Reflection of Light

6.2.4Refraction of Light

6.2.5Refraction of Light 2

6.2.6Internal Reflection

6.3Sound Waves

6.3.1Sound Waves

6.3.2Sound Waves & our Ears

6.3.3Speed of Sound

6.3.4Speed of Sound Experiment

6.3.5Sound as a Wave

6.3.6Uses of Sound Waves: Ultrasound Waves

6.3.7Uses of Sound Waves: Earthquakes

6.3.8Sound Waves - Calculations

6.3.9End of Topic Test - Introduction to Waves

6.3.10Exam-Style Questions - Wave Speed

6.4Electromagnetic Waves

6.4.1Properties of Electromagnetic Waves

6.4.2Gamma Rays

6.4.3X-Rays

6.4.4UV Light

6.4.5Infrared Radiation

6.4.6Microwaves

6.4.7Radio Waves

6.4.8Properties 2

6.4.9Visible Light

6.4.10Visible Light 2

6.4.11Specular & Diffuse Reflection

6.4.12Colours

6.4.13Grade 9 - Waves

6.5Lenses

6.5.1Lenses

6.5.2Convex Lens

6.5.3Concave Lens

6.5.4Lenses - Calculations

6.5.5Images

6.5.6Ray Diagrams

6.5.7Ray Diagrams 2

6.6Heat & Radiation

6.6.1Infrared Radiation

6.6.2Radiation & Surface Colour

6.6.3Surface Area & Temperature

6.6.4Temperature

6.6.5Absorption & Emission

6.6.6Greenhouse Effect

6.6.7Energy Balance of the Earth

6.6.8End of Topic Test - EM Waves, Lenses & Heat

6.6.9Exam-Style Questions - EM Radiation

7Magnetism

7.1Magnetism Basics

7.1.1Magnetism

7.1.2Magnetic Materials

7.1.3Induced Magnetism

7.1.4Magnetic Fields

7.1.5Magnetic Field Patterns

7.2Electromagnetism

7.2.1The Magnetic Effect of a Current

7.2.2Solenoid Field

7.2.3Magnetic Field Strength

7.2.4Uses of Electromagnets

7.2.5Motor Effect

7.2.6Direction of Motor Effect

7.2.7Magnetic Flux Equation

7.2.8Magnetic Flux - Calculations

7.2.9Electric Motors

7.2.10Loudspeakers

7.2.11Force Acting on a Coil in a Magnetic Field

7.2.12Induced Potential Difference

7.2.13Increasing the Induced Potential Difference

7.2.14Magnetic Field Direction

7.2.15Forces Between Electricity & Magnets

7.2.16AC/DC

7.2.17AC Generators

7.2.18Generator Effect

7.2.19Microphones

7.3Transformers

7.3.1Transformers

7.3.2Transformer Equation

7.3.3Step-Up & Step-Down Transformers

7.3.4Principles of Transformer Operation

7.3.5High-Voltage Transmission & Transformers

7.3.6Energy in Transformers

7.3.7Power Losses in Cables

7.3.8Transformers - Calculations

7.3.9Transformers 2 - Calculations

7.3.10End of Topic Test - Magnetism

7.3.11Grade 9 - Transformers

7.3.12Exam-Style Questions - Magnetic Fields

8Astrophysics

8.1Astrophysics

8.1.1The Solar System

8.1.2The Sun

8.1.3The Solar System - Calculations

8.1.4Orbits

8.1.5Stable Orbits

8.1.6Orbits HyperLearning

8.1.7Life Cycle of a Star like the Sun

8.1.8Life Cycle of a Star Much Bigger than the Sun

8.1.9Creation of Elements

8.1.10Red-shift

8.1.11The Big Bang Theory

8.1.12Gaps in Knowledge

8.1.13End of Topic Test - Astrophysics

8.1.14Exam-Style Questions - Astrophysics

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