Energy

Energy exists in different stores and is transferred between them during events and processes. The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one store to another.

Types of energy store

Energy can be stored in different ways depending on the nature of the object and its surroundings. Below are the main types of energy stores, along with real-life examples.

• Kinetic Energy - The energy of moving objects - For example, A moving car or a running athlete.

• Gravitational Potential Energy (GPE) - Energy stored in an object due to its height above the ground - For example, A book on a shelf or a skier at the top of a hill.

• Chemical Energy - Stored in substances such as fuels, food, and batteries, and released during chemical reactions - For example, Gasoline, food, or a charged battery.

• Elastic (Strain) Energy - Stored in stretched or compressed objects that can return to their original shape - For example, A stretched rubber band or a compressed spring.

• Nuclear Energy - Stored in atomic nuclei and released during nuclear reactions - For example, Nuclear power plants and the Sun’s fusion process.

• Electrostatic Energy - Stored due to interactions between electric charges - For example, A charged balloon sticking to a wall.

• Internal (Thermal) Energy - Stored due to the temperature of an object, consisting of both kinetic and potential energy of particles - For example, Boiling water or a hot coffee cup.

Energy transfers

Energy is transferred from one store to another through different mechanisms. These transfers occur during various physical processes and interactions.

Methods of Energy Transfer:

• Mechanical Work - Energy is transferred when a force moves an object - For example, Pushing a shopping trolley.

• Electrical Work - Energy is transferred by an electric current - For example, A light bulb turning on.

• Heating - Energy is transferred due to a temperature difference between objects - For example, Boiling water in a kettle.

• Radiation (Waves) - Energy is transferred by light, sound, or electromagnetic waves - For example, Sunlight heating the Earth or radio waves carrying signals.

Examples of energy transfers

To illustrate how energy moves between stores, consider the following examples:

A Ball Falling

• Energy Transfer:

  • Gravitational Potential Energy (GPE) → Kinetic Energy

  • As the ball falls, its gravitational potential energy decreases, and kinetic energy increases as it accelerates.

  • When it hits the ground, some energy is transferred into sound and heat.

A Car Braking

• Energy Transfer:

  • Kinetic Energy → Thermal Energy

  • As a car slows down, its kinetic energy is converted into heat due to friction in the brakes.

A Pendulum Swinging

• Energy Transfer:

  • Gravitational Potential Energy (at the highest point) → Kinetic Energy (at the lowest point).

  • In an ideal system (no air resistance), this process repeats indefinitely. In reality, energy is lost as heat and sound due to friction.

Conservation of energy