Energy exists in many forms including potential, kinetic, chemical, and electromagnetic. Potential energy is stored energy and includes gravitational potential energy from an object's position and strain energy stored through deformation. Kinetic energy is the energy of motion and includes sound, electrical, internal, electromagnetic, and light energy. Energy can change forms and is never lost or destroyed, though some is always wasted as heat. Common sources of energy include both renewable resources like sunlight and non-renewable resources like fossil fuels.

1. Energy
Chapter 15
Physics

2. What is energy?
There are many forms
of energy

3. Kinds of energy
Stored energy
(Potential energy)
Movement energy
(Kinetic energy)

4. Types of potential energy
Gravitational
potential energy
Strain energy Chemical energy

5. 1) Gravitational potential energy
- The force of gravity between the object and the earth
pulls the object towards the centre of the planet.
- If an object is in a position above the surface of the
Earth, it possesses stored energy called gravitational
potential energy.

6. - Example:
- Plates on a table (if the support is removed it will
accelerate to the earth’s surface)
- The potential energy is released when an object falls
and changes to other forms of energy.

7. Stored Mechanical Energy
- Energy stored in an object by the
application of force
- Must push or pull on an object.
- When the shape of elastic
materials is changed by bending,
squashing or stretching they store
energy which allows them to return
back to its original shape.
2) Strain energy (Elastic energy)

8. - Energy stored in the bonds between atoms.
- Holds molecules together.
- Food, fuel and chemicals stored in an
electrical cell (battery) are examples
containing stored chemical energy.
- Energy is released when the links are
broken down.
3) Chemical energy

9. - Ex. During respiration, carbohydrates are
broken down into co₂ and water. The energy
that is released in this process is used to keep
your body alive.
- Energy is released by fuels to heat homes, for
production of new materials, to heat water,
etc..

10. Mechanical Energy
(Motion)
Movement of objects or
substances from one
place to another
Kinetic
Energy

11. Types of kinetic energy
Sound
energy
Electrical
energy
Internal
energy
Electro-
magnetic
energy
Light
energy

12. - Movement of energy through
substances in the form of longitudinal
(compression) waves due to vibration
of an object.
- Sound energy can pass through
solids, liquids and gases.
1) Sound energy

13. - Electric current is the movement of
electric charges through a conductor.
- Electric charges are given electrical
energy by the battery, and is carried to
all working parts of a circuit.
- Ex. In the lamp, the electrical energy
is changed into heat and light energy.
2) Electrical energy

14. - All substances are made up of
particles and possess a certain
amount of energy.
- When a substance is heated the
amount of energy increases.
3) Internal energy (thermal energy)

15. - It is a form of energy that can travel through space at the speed
of light.
- This kind of energy travels in waves that have some properties
of electricity and some properties of magnetism.
- As these waves make up rays of light and heat, it is sometimes
called radiation energy.
- They have different wavelengths.
4) Electromagnetic energy

17. - Light is the energy we can see.
- Light energy from the sun can be
spread out by a prism or a shower of
raindrops into light of different
wavelengths (rainbow)
5) Light energy

18. - When energy is used it always
changes from one form to another
and some always change into heat
energy.
Energy changes

19. - When we turn on the lamp the
electrical energy changes into light
energy which is useful to us and heat
energy (wasted).
- For example: Some machines make
so much noise (wasted sound energy)
that people using them have to wear
ear protection
Wasted energy

20. Sources of energy
Renewable resources Non-renewable resources