Energy

Chapter 15Physics

What is energy?

There are many forms of energy

Kinds of energy

Stored energy (Potential energy)

Movement energy (Kinetic energy)

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

Kinetic Energy

Types of kinetic energy

Sound energy

Electrical energy

Internal energy

Electro-magnetic energy

Light energy

- 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

- 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

- 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)

- 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

- 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

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

Energy changes

- 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

Sources of energy

Renewable resources Non-renewable resources

Types of potential energy

Gravitational potential energy

Strain energy Chemical energy

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.

- 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.

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)

- 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

- 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..