Energy

Chapter 38

What is Energy?

• Energy is the ability to do work.

• The unit of energy is the Joule(J).

Different forms of Energy

Potential Energy-stored energy in a body.eg coiled spring

Kinetic Energy- energy that moving objects have.

Heat Energy-Hot air rises.

Light Energy-Crooks radiometer or solar powered calculator.

Sound Energy-

Electrical Energy-may be converted to Light, heat sound.

Chemical Energy-energy stored in food, oil etc.

Nuclear Energy-Energy released from the nuclei of atoms.

Law of Conservation of Energy

• Energy cannot be created or destroyed, but can only change from one form to another

Energy can be changed from one form to another.

For example:

Chemical energy in food is converted to thermal energy

and kinetic energy by our bodies.

Energy transfer

What other energy transfers can you think of?

Gravitational energy in a ball is converted to kinetic energy when it falls to the ground.

burning match portable torch microphone radio television catapult mobile phone

car

chemical → heat and light

chemical → heat and light

sound → electrical

electrical → sound and heat

electrical → sound and light and heat

elastic → kinetic and heat

chemical → sound and microwaves (EM radiation) and heat

chemical → kinetic and sound and heat

In all these transfers the energy is not lost, it is conserved. Energy cannot be destroyed or created.

What energy transfer takes place in each device?

What is the energy transfer?

Name the Energy Conversions?

Energy needs and Heat Loss

Heat loss in a House where noprecautions have been taken to save Heat.

Glass Fibre on the attic floor

Lagging on hot water tank and pipes

Air cavity wall insulation

Draught excluders on doors and Windows

Double Glazing on windows

Sources of Energy

The Energy sources used to produce the worlds electricity

Non renewable sources of energy • Non renewable sources of energy are fossil

fuels (coal, oil, natural gas). Once used they cannot be replaced.

How we have used fossil fuels over the centuries.

This is how long coal, gas and oil will last if we continue to use them at the present rate.

Fossil fuel reserves

Renewable sources of energy

Renewable sources of energy are those that will never be used up.

Examples:Solar energyHydro-electric energyWind energyWave energyBiomass energy-trees and plantsTidal energy

Geothermal Energy-heat from ground

Hydro-electric power

What is Biomass?

Biomass energy comes from trees and plants.

In this diagram plants are being broken down by bacteria to produce methane(natural gas)

What is Geothermal energy?

Geothermal energy is energy that is got from the ground.

The hot water or steam that is got from the ground is sent to turbines to produce electricity.

Iceland uses a lot of geothermal energy.

Schematic representation of an ideal geothermal system.

The Sun

• The Sun is the primary source of Energy.

• Energy radiated to the earth in the form of light and Heat provides us with all of the energy we use.

Most of the energy on the Earth comes from the Sun. Energy is converted from one form to another. Eventually the Energy is wasted or spreads out, usually in the form of heat sound or light.

Energy from the sun

Nuclear Energy

• Nuclear energy is the energy released from the nuclei of atoms.

Nuclear fission is used in electric power stations.

This involves the splitting of large atoms like Uranium, and the enormous energy released is converted to electrical energy.

Nuclear fusion

• Nuclear fusion occurs in the sun. Here nuclei of light atoms combine to produce enormous amounts of energy.

How a nuclear reactor works

Advantages and dis-advantages of nuclear energy

Advantages– Medicine-kill cancer cells.– Radiation sterilises food.– Production of Electricity – Will not run out like fossil fuels

Disadvantages– Difficult to get rid of waste– Radiation can kill– Accidents like Chernoble