Physics GCSE: Energy Transfers

Revision Summary

Types of energy

Energy can not be created or destroyed it can only change from one form into another.

There are many types of energy including,

·         sound

·         heat

·         light

·         kinetic

·         nuclear

·         potential energy

Kinetic energy is movement energy. Potential energy is stored energy. There are three main forms of potential energy including gravitational, chemical and elastic.

Sankey diagrams can be used to represent energy changes. The size of the arrows represents the amount of that type of energy.

Energy is measured in Joules, J or kilojoules, kJ.

Conduction

Heat energy always moves from hotter objects to colder objects.

Heat energy is conducted through solids by particles vibrating and passing on the movement to neighbouring particles.

Metals are best at conducting heat. As well as the vibrating particles, they move the heat energy by free electrons moving between their atoms.

The poorest conductors are gases as their molecules are too far apart to affect each other much.

Air is a very bad conductor. Most insulators work because of trapped air.

Convection

Convection is hot gases or liquids rising and cooler gases and liquids sinking to replace it. As substances heat up the density decreases, which is what makes them float.

This movement of molecules is called a convection current. It can only happen in a gas or liquid where the molecules are free to move around.

Radiation

Radiated heat energy is infrared radiation. All hot objects radiate heat.

Black, dull surfaces are the best emitters of heat radiation. Lighter, shinier surfaces are poor radiators of heat.

Radiated heat can also be absorbed by cooler objects. Black is the best absorber. Surfaces coloured silver or white will reflect the radiated heat.

Ways to save energy in the home

Reducing heat losses from a home means less damage to the environment and lower heating bills.

Installing insulation costs money. The payback time is how long it takes for the savings to cover the cost.

Each strategy has to reduce conduction, convection, radiation or any combination of them.

Common strategies are double-glazing, loft insulation, tank lagging, lined curtains, cavity wall insulation, blocking up disused fireplaces and putting foil behind radiators.

Other conservation strategies include using of low-energy light bulbs, turning down heating thermostats, fitting draught excluders and switching off unattended appliances.

Non-renewable fuels and power stations

The fossil fuels are oil, gas and coal. They are non-renewable, which means that they can not be replaced. They will eventually run out.

These fuels have many uses but the main ones are heating, transport and generating electricity.

In power stations, the fuel is burnt and the heat turns water into steam. That steam pushes around a turbine that is connected to a generator. The generator produces electricity.

This process is the same for all power stations.

Nuclear power stations don't burn the fuel. Uranium fuel generates heat that turns water into steam just like in other power stations.

Nuclear accidents are rare, but can be serious. The waste from the reactors can be radioactive. It is easy to store it safely for now but it will stay radioactive for years.

Environmental impacts of burning fuels

Carbon dioxide is the most common of several gases that contribute to the greenhouse effect. The result is global warming. This would result in the weather being more extreme and the ice caps melting raising the sea levels.

Sulphur dioxide is the most common cause of acid rain. It dissolves in rainwater to form an acid. The acid rain harms plants, animals and stonework.

Alternative energy sources

Most of the alternative energy sources are renewable. This means there is either an endless supply of them so that they will not run out, or they can be easily replaced.

Hydroelectric power is only possible where the geology is right, such as Scotland. Water runs fast down an incline and turns a turbine.

Some developing countries get all their energy from HEP schemes on large dams. The large lake made behind the dam drastically alters the surroundings.

Waves and tides have a lot of energy. Few schemes exist because of technological problems and environmental objections.

Solar power converts the suns energy into electricity using solar panels. These panels are expensive to make.

Wind farms are groups of wind turbines that generate electricity from wind. Some people don't like wind farms because they spoil the view or make a noise.

Geothermal energy uses the natural heat in volcanic rock to generate electricity.

Gas called methane is produced when matter rots. This gas can be used to generate heat to produce electricity.

Burning rubbish is not a way to avoid pollution but it does preserve fossil fuels as well as avoid rubbish having to be put in landfill sites.

Crops can be grown to be burnt in a power station. Another version of this is to process the crops into alcohol and use it instead of petrol in cars.