1.1.6
Energy Transfers
Conservation of Energy
Conservation of Energy
The principle of the conservation of energy says that energy cannot be created or destroyed. It can only be transferred from one store of energy into another. Energy can be transferred by:
Mechanical work
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
Electrical work
- An electrical current transfers energy from one object to another, such as a battery powering a torch.
Heating
Heating
- Heating an object transfers energy to the object's internal store of energy (the sum of the energy in the kinetic and chemical stores of its particles).
Waves
Waves
- Light and other types of waves can transfer energy from one object to another.
Examples of Energy Conversion
Examples of Energy Conversion
Energy is never created or destroyed, only converted from one store to another. Here are some examples of this process:
A moving object hitting an obstacle
A moving 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.
An object projected upwards
An object projected upwards
- The object's energy is initially in the kinetic store as it moves upwards.
- The object's energy is slowly transferred from the kinetic store to the gravitational potential store as it slows down and climbs higher.
- Once the object reaches its highest point, all of its energy is in the gravitational potential store.
- As the object falls again, energy transfers from the gravitational potential store to the kinetic store.
A vehicle slowing down
A vehicle slowing down
- To begin with, the vehicle's energy is in the kinetic store.
- The brakes do work slowing the car down. During this process, energy is dissipated (lost) through heat and sound.
Bringing water to a boil in an electric kettle
Bringing water to a boil in an electric kettle
- Energy transfers from the electrical store of the mains power supply to the thermal store of the water.
An object accelerated by a constant force
An object accelerated by a constant force
- Work is done by a force on an object.
- This work is converted to the object's kinetic store.
1Energy
1.1Energy Changes
1.1.1Energy Stores
1.1.2Calculating Changes in Energy
1.1.3Changes in Kinetic Energy - Calculations
1.1.4Changes in GPE - Calculations
1.1.5Changes in EPE - Calculations
1.1.6Energy Transfers
1.1.7Mechanical Work Done
1.1.8Mechanical Work - Calculations
1.1.9Electrical Work Done
1.1.10Electrical Work Done- Calculations
1.2Energy Losses & Efficiency
2Electricity
2.1Electric Charge
2.2Resistance & Electrical Work
2.3Electric Circuits
2.4Electricity in Homes
2.5Static Electricity
3Particle Model of Matter
3.1States of Matter
3.2Heat
4Atoms & Radiation
4.1Atoms
4.2Radiation
4.2.1Radioactive Decay
4.2.2Radioactive Decay 2
4.2.3Types of Radioactive Emission
4.2.4Fission & Fusion
4.2.5Radioactive Decay Equations
4.2.6Radio. decay equations - Calculations
4.2.7Half Lives & Ionising Radiation
4.2.8Half Life - Calculations
4.2.9Uses & Dangers of Radiation
4.2.10Uses & Dangers of Radiation 2
4.2.11End of Topic Test - Atoms & Radiation
4.2.12Grade 9 - Radiation
4.2.13Exam-Style Questions - Radioactive Decay
5Forces
5.1Basics of Motion
5.2Forces
5.2.1Gravity
5.2.2Gravity - Calculations
5.2.3Resultant Forces
5.2.4Newton Second Law - Calculations
5.2.5Force Diagrams
5.2.6Free Body Diagrams - Calculations
5.2.7Stretching a Spring
5.2.8Hooke's Law
5.2.9Hooke's Law - Calculations
5.2.10Elastic Potential Energy
5.2.11Elastic Potential - Calculations
5.2.12Exam-Style Questions - Elastic Potential Energy
5.3Effects of Forces
6Waves
6.1Wave Basics
6.2Waves at a Boundary
6.3Sound Waves
6.4Electromagnetic Waves
7Magnetism
7.1Magnetism Basics
7.2Electromagnetism
Jump to other topics
1Energy
1.1Energy Changes
1.1.1Energy Stores
1.1.2Calculating Changes in Energy
1.1.3Changes in Kinetic Energy - Calculations
1.1.4Changes in GPE - Calculations
1.1.5Changes in EPE - Calculations
1.1.6Energy Transfers
1.1.7Mechanical Work Done
1.1.8Mechanical Work - Calculations
1.1.9Electrical Work Done
1.1.10Electrical Work Done- Calculations
1.2Energy Losses & Efficiency
2Electricity
2.1Electric Charge
2.2Resistance & Electrical Work
2.3Electric Circuits
2.4Electricity in Homes
2.5Static Electricity
3Particle Model of Matter
3.1States of Matter
3.2Heat
4Atoms & Radiation
4.1Atoms
4.2Radiation
4.2.1Radioactive Decay
4.2.2Radioactive Decay 2
4.2.3Types of Radioactive Emission
4.2.4Fission & Fusion
4.2.5Radioactive Decay Equations
4.2.6Radio. decay equations - Calculations
4.2.7Half Lives & Ionising Radiation
4.2.8Half Life - Calculations
4.2.9Uses & Dangers of Radiation
4.2.10Uses & Dangers of Radiation 2
4.2.11End of Topic Test - Atoms & Radiation
4.2.12Grade 9 - Radiation
4.2.13Exam-Style Questions - Radioactive Decay
5Forces
5.1Basics of Motion
5.2Forces
5.2.1Gravity
5.2.2Gravity - Calculations
5.2.3Resultant Forces
5.2.4Newton Second Law - Calculations
5.2.5Force Diagrams
5.2.6Free Body Diagrams - Calculations
5.2.7Stretching a Spring
5.2.8Hooke's Law
5.2.9Hooke's Law - Calculations
5.2.10Elastic Potential Energy
5.2.11Elastic Potential - Calculations
5.2.12Exam-Style Questions - Elastic Potential Energy
5.3Effects of Forces
6Waves
6.1Wave Basics
6.2Waves at a Boundary
6.3Sound Waves
6.4Electromagnetic Waves
7Magnetism
7.1Magnetism Basics
7.2Electromagnetism
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