ENERGY
Meaning of energy
Energy is the capacity to do work. This means anything that can cause change or make something move has energy.
Examples: lifting a book, boiling water, or running all require energy.
Unit of measurement: Joule (J).
Sources of Energy
Energy can be obtained from natural sources (found in the environment) and artificial sources (made or controlled by humans).
A. Natural Sources of Energy
- Sunlight: Provides solar energy used for warmth, drying, and electricity via solar panels.
- Food: Plants and animals store chemical energy which our bodies convert into energy for movement and work.
- Water: Flowing water has kinetic energy that can be converted into electricity using hydroelectric turbines.
- Wind: Moving air has kinetic energy that can turn wind turbines to generate electricity.
- Fossil fuels: Coal, crude oil, and natural gas release energy when burned.
- Wood: Burning wood releases chemical energy as heat and light.
B. Artificial Sources of Energy
- Batteries: Contain chemical energy that can be converted to electrical energy for devices.
- Electric generators: Convert mechanical energy from turbines into electrical energy.
- Petroleum products: Fuels like petrol, diesel, and kerosene release energy when burned.
Types of Energy
Energy exists in different forms, and one form can change into another.
A. Mechanical Energy
Potential Energy (PE): Stored energy due to the position of an object.
Example: A book on a shelf has potential energy because of its height.
Formula: PE = m × g × h, where m = mass, g = acceleration due to gravity (~10 m/s²), h = height above the ground.
Kinetic Energy (KE): Energy of a moving object.
Example: A rolling ball has kinetic energy because it is moving.
Formula: KE = 1/2 × m × v², where v = speed of the object.
B. Heat (Thermal) Energy
Energy due to the movement of tiny particles (atoms and molecules) in a substance. Faster-moving particles mean more heat energy.
Example: Boiling water or a heated iron.
C. Light (Radiant) Energy
Energy carried by light rays that can be seen or absorbed.
Example: Sunlight, torchlight, or laser light.
D. Sound Energy
Energy produced when objects vibrate. Vibrations travel as waves through air, water, or solids.
Example: A drum beating or a ringing bell.
E. Chemical Energy
Energy stored in chemical bonds of substances, released during chemical reactions.
Example: Energy in food, fuel, or batteries.
F. Electrical Energy
Energy produced by the flow of electric charges through conductors.
Example: Powering a fan, television, or phone charger.
G. Nuclear Energy
Energy stored in the nucleus of atoms. Released when the nucleus is split (fission) or combined (fusion).
Example: Nuclear power plants or the sun.
Renewable and Non-Renewable
Renewable Energy
Sources that can be naturally replenished and will not run out if managed properly.
Examples:
- Sunlight → Solar energy
- Wind → Wind energy
- Flowing water → Hydroelectric energy
- Biomass → Energy from plants or organic waste
Non-Renewable Energy
Sources that cannot be easily replaced once used.
Examples:
- Coal
- Crude oil
- Natural gas
- Nuclear fuels
Examples of Energy Sources
- Solar panels → Convert sunlight to electricity
- Wind turbines → Convert wind to electricity
- Hydroelectric dams → Convert moving water to electricity
- Fossil fuels → Burned to produce heat, electricity, and fuel for transport
- Food → Gives energy to the body for daily activities
- Batteries → Provide energy for devices like torches, radios, and phones
Uses of Energy
Energy is essential in everyday life, industry, and society.
- Electricity generation – Powers homes, schools, factories, and offices
- Heating and cooking – Stoves, ovens, irons, and water heaters
- Transport – Cars, buses, trains, and airplanes need energy to move
- Industry – Machines, tools, and equipment use energy for production
- Communication – Phones, computers, radios, and TVs
- Body functions – Food energy is converted into energy for movement, growth, and work
Implications of Misuse of Energy
- Pollution of air, water, and soil
- Global warming and climate change from burning fossil fuels
- Depletion of non-renewable resources
- Accidents and injuries from improper use of electricity or fuels
Energy Transformation
Energy can change from one form to another, but it cannot be created or destroyed.
Law of Conservation of Energy: Total energy remains the same; it only changes forms.
Examples of Energy Transformation:
- Electrical → Heat: Electric iron, stove
- Electrical → Light: Light bulb
- Chemical → Electrical: Battery
- Electrical → Kinetic: Fan
- Mechanical → Electrical: Bicycle dynamo
Energy and Society
Energy is crucial for daily life and industrial activities. Lack of energy disrupts work and productivity.
Example: In welding, lack of electricity or fuel prevents the welding machine from working, which stops metal fabrication and slows construction projects.
Energy shortage can affect homes, schools, factories, and transport systems.
Work and Power
Work: Done when a force moves an object over a distance.
Formula: Work = Force × Distance
Power: Rate at which work is done or energy is used.
Formula: Power = Work ÷ Time
Unit: Watt (W)
Conservation of Energy
- Using energy wisely ensures it lasts longer and reduces environmental damage
- Renewable energy sources should be promoted for sustainable living
- Efficiency prevents wastage and reduces costs
Summary
- Energy is the capacity to do work
- It exists in many forms: mechanical, heat, light, sound, chemical, electrical, and nuclear
- Energy comes from renewable and non-renewable sources
- Energy is needed for homes, industry, transport, and the human body
- Misuse of energy causes environmental harm and resource depletion
- Conservation and efficient use of energy are essential for society
