Topics
What is Energy?
In physics, energy is defined as the capacity to do work. It’s a scalar quantity (has magnitude but no direction) and is central to understanding how physical systems evolve and interact.
SI Unit of Energy
Joule (J): Named after James Prescott Joule.
1 Joule = Work done by a force of 1 Newton moving an object 1 meter.
Other units include:
- Calorie
- Kilowatt-hour (kWh)
- Electronvolt (eV)
Types of Energy
Kinetic Energy
Energy of motion.
Potential Energy
Stored energy due to position or configuration. PE = mgh
Thermal Energy
Due to random motion of particles – related to temperature and heat.
Chemical Energy
Stored in atomic bonds – released during reactions (e.g., combustion).
Electrical Energy
From movement of electrons – power circuits and devices.
Radiant Energy
Carried by electromagnetic waves (e.g. sunlight, X-rays).
Nuclear Energy
Stored in atomic nuclei – released via fission or fusion.
Law of Conservation of Energy
Energy can neither be created nor destroyed, only transformed from one form to another.
Energy Transformations
Energy can change forms obeying Law of Conservation of Energy.
- Chemical → Thermal (burning fuel)
- Electrical → Mechanical (electric motor)
- Potential → Kinetic (falling object)
Real-World Applications
- Engineering: Designing efficient machines and engines.
- Biology: Understanding metabolism and ATP energy cycles.
- Climate Science: Tracking heat transfer and energy balance.
- Technology: Powering devices, batteries, and renewable systems.
Glossary of Key Terms
Recap of the Key Terms in Energy
- Energy: The capacity to do work or produce change.
- Joule (J): SI unit of energy; 1 J = 1 N·m.
- Kinetic Energy: Energy of motion.
- Potential Energy: Stored energy due to position.PE = mgh
- Mechanical Energy: Sum of kinetic and potential energy in a system.
- Thermal Energy: Energy from random motion of particles, related to heat.
- Chemical Energy: Energy stored in chemical bonds.
- Electrical Energy: Energy from moving electric charges.
- Nuclear Energy: Energy stored in atomic nuclei, released via fission or fusion.
- Radiant Energy: Energy carried by electromagnetic waves (e.g., light).
Quiz
Recap the concepts you have learnt. Try to answer the questions. You can find the answer to any question by clicking on the icon.
What is the difference between kinetic and potential energy?
Kinetic energy is due to motion. Potential energy is due to position or configuration.
Can energy be destroyed?
No. According to the Law of Conservation of Energy, it can only change forms.
What happens to energy in a closed system?
It remains constant. Energy may transform but the total amount stays the same.
How is energy measured?
In joules (J). Other units include calories, kilowatt-hours, and electronvolts.
What type of energy does a battery store?
Chemical energy, which is converted to electrical energy when used.
What is mechanical energy?
The sum of kinetic and potential energy in a system.
Why is power important in energy studies?
Power is important in Energy studies because it tells us how quickly energy is used or transferred.
What’s an example of energy transformation?
A hydroelectric dam converts potential energy of water into electrical energy.