Energy and Its Types

Definition and Units of Energy

• Energy is the capacity to do work or produce change, existing in various forms that can be transformed from one to another.
• Units of measurement: Joules (J), Calories (cal), Kilowatt-hours (kWh)

Types of Energy

Kinetic Energy

• Energy of motion
• Formula: KE = 1/2 mv^2 (where m is mass and v is velocity)

Potential Energy

• Energy stored due to position or configuration
• Gravitational Potential Energy: PE = mgh (where m is mass, g is gravitational acceleration, and h is height)
• Elastic Potential Energy: PE = 1/2 kx^2 (where k is the spring constant and x is displacement)

Other Types of Energy

• Thermal Energy: related to the temperature of an object, the kinetic energy of its molecules
• Chemical Energy: stored in chemical bonds, released or absorbed during chemical reactions
• Electrical Energy: due to the movement of electric charges
• Nuclear Energy: stored in the nucleus of atoms, released during nuclear reactions
• Radiant Energy: carried by electromagnetic waves (e.g., light, X-rays)

Laws of Energy

Law of Conservation of Energy

• Energy cannot be created or destroyed, only transformed from one form to another
• Total energy in a closed system remains constant

First Law of Thermodynamics

• Change in internal energy of a system equals heat added to the system minus work done by the system

Second Law of Thermodynamics

• Energy transfers or transformations increase the entropy (disorder) of the universe
• Heat energy naturally flows from hotter to cooler objects

Third Law of Thermodynamics

• As temperature approaches absolute zero, entropy of a perfect crystal approaches zero

Energy Transformations

• Mechanical to Electrical: generators convert mechanical energy into electrical energy
• Chemical to Thermal: burning fossil fuels releases chemical energy as heat
• Electrical to Mechanical: electric motors convert electrical energy into mechanical energy
• Radiant to Chemical: photosynthesis converts sunlight into chemical energy in plants

Energy Sources

Renewable Energy

• Solar: energy from the sun, captured using photovoltaic cells or solar thermal systems
• Wind: energy from wind, harnessed using wind turbines
• Hydro: energy from flowing water, captured using dams and turbines
• Biomass: energy from organic materials
• Geothermal: energy from the heat inside the Earth

Non-Renewable Energy

• Fossil Fuels: coal, oil, natural gas
• Nuclear: energy from nuclear reactions, typically fission of uranium or plutonium

Applications of Energy

Residential

• Heating, cooling, lighting, and powering appliances

Industrial

• Manufacturing processes, machinery operation, chemical production

Transportation

• Fuel for vehicles (gasoline, diesel, electric batteries)

Commercial

• Energy for buildings, offices, shops, and services

Energy Efficiency and Conservation

Energy Efficiency

• Using technology that requires less energy to perform the same function (e.g., LED lighting, high-efficiency appliances)

Energy Conservation

• Reducing energy consumption through behavioral changes (e.g., turning off lights, reducing thermostat settings)

Environmental Impact of Energy Use

Pollution

• Burning fossil fuels releases pollutants (e.g., CO2, NOx, SOx) contributing to air pollution and climate change

Resource Depletion

• Overuse of non-renewable resources leads to their depletion and potential shortages

Habitat Destruction

• Energy extraction processes can harm ecosystems (e.g., mining, drilling)

Climate Change

• Greenhouse gas emissions from energy use are a major contributor to global warming and climate change