ENERGY

  • Energy is known as the ability to do work, or produce a change. Energy is measured in joules (J). 

  • When work is done, energy is converted from one form to another. Energy can’t be created or destroyed, it can only be transformed.

  • There are two main types of energy: POTENTIAL energy and KINETIC energy.

  • Potential energy is energy that’s stored. It can be used at a later time and depends on what a substance is made of and where it is.

  • Kinetic energy is energy that comes from movement. The faster an object moves, the more kinetic energy it has. 

  • Almost all forms of energy come from these two main types.


Kinetic energy form

Description

Thermal (heat) energy

Thermal energy comes from the movement of atoms and molecules. The faster these particles move, the more heat energy is present.

Mechanical energy 

Mechanical energy comes from an objects position and movement 

Electrical energy 

Electrical energy or electricity comes from the movement of charged particles through a wire.

Magnetic energy 

Magnetic energy comes from the push and pull of a magnetic field.



Potential energy form

Description 

Chemical potential energy 

Chemical energy is stored in food, or fuel. It is stored in the bonds of molecules

Elastic potential energy

Elastic energy is stored in substances that are being stretched or compressed

Nuclear potential energy

Nuclear energy is stored in the nucleus of large and unstable atoms.

Gravitational potential energy 

Gravitational energy is stored in objects that are high positions over the earth’s surface. 



 Conservation of energy, and energy transfer


  • Any change that happens in the universe requires energy to occur. In order for any work to be done, energy must be exerted.

  • When we do work, energy is converted from one form to another.

  • The law of conservation of energy states that energy is neither created nor destroyed, only converted from one form to another, or transferred from one object to another.

  • Examples of energy transfer:

    • If a metal spoon is in a hot cup of tea or coffee, the spoon will also get hot. This happens because heat energy is transferred from the tea to the spoon. 

    • In an electric circuit, electrons (and electrical energy) flow around the circuit. They are transferred from one place to another.

  • Examples of energy transformations

    • When an appliance such as an iron, or kettle is switched on, the electrical energy is converted to heat energy, allowing for them to get hotter.

    • In almost all fuels, the chemical energy stored in the bonds between the atoms is converted to other forms of energy such as kinetic energy (in vehicles), along with heat, light and sound energy.

    • In energy sources like wind, tidal and hydroelectricity, the kinetic energy of these mediums is converted to electrical energy that can help to power different processes.


Wasted Energy

  • Not all energy conversions are 100% efficient. This means that some of the energy will be converted to an unwanted or unintended form.

  • Efficiency refers to the fraction of energy that’s used to do useful or intended work. It is expressed as a percentage and can let us know how well a device or system converts energy from one form to another.

  • In general, energy transformations can be represented by this equation:
    ENERGY INPUT → ENERGY OUTPUT

    • Going further, it can be said that energy input gives rise to useful and wasted energy.

      • ENERGY INPUT → USEFUL ENERGY + WASTED ENERGY 

      • For example, in a lightbulb, electrical energy → light energy + heat energy

      • The light energy is useful because it allows the light bulb to produce light, but heat energy is wasted.