1.2.1
Energy Losses & Efficiency
Wasted Energy
Wasted Energy
When one store of energy is transferred to another, some energy is wasted (transferred into unwanted stores of energy). This dissipates (spreads out) to anything nearby.
Car engines - noise and heat
Car engines - noise and heat
- Car engines make a lot of noise and get hot when they are being used to move you about.
- The useful energy store here is the kinetic store because you want the car to move you from one place to another.
- The heat and sound energy are wasted energy because they are of no use to you.
Wires - heat
Wires - heat
- When wires are used in an electrical circuit, they heat up.
- This is often not useful energy and so it is wasted.
Friction - heat
Friction - heat
- In almost every energy transfer, friction creates heat energy and this energy is often wasted.
Efficiency of Energy Transfer
Efficiency of Energy Transfer
The efficiency of an energy transfer can never be more than 100. It is defined below:
Efficiency (energy in joules)
Efficiency (energy in joules)
- Efficiency = (useful energy output/total energy input) x 100
- The useful energy output and total energy input are measured in joules (J).
Efficiency (power in watts)
Efficiency (power in watts)
- Efficiency = (useful power output/total power input) x 100
- The useful power output and total power input are measured in watts (W).
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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