Power
Energy and Thermal Physics

Energy and generating electricity

Teaching Guidance for 14-16 PRACTICAL PHYISCS

In discussing energy in everyday life, mains electricity is almost certain to come up. Mains electricity transfers energy from power stations to devices we use every day. 

Electricity is generated using an resource such as a fossil fuel or uranium (a nuclear fuel). This is important to any discussion of the greenhouse effect, global warming, or climate change

Discussion of ‘resources’ for generating electricity might lead on to so-called ‘renewable’ resources such as wind, sunlight and waves. ‘Wind energy’ and ‘solar energy’ are in everyday use. However, it is more useful to refer to 'wind power' and 'solar power', as the 'power' designation more accurately refers to the process of transferring energy per second.

The process of generating electricity, or using any device that needs an electric current, will dissipate energy, and heat up the surroundings. The fuels used to generate electricity are used up in the process, and are used up more quickly if a lot of energy is dissipated.

‘Save it’

The approach described above provides a good platform for later discussions of 'energy saving', especially domestic energy saving. The idea of 'energy saving' can seem strange to students who understand that 'energy is conserved'. If it is conserved, why is there a need to save it?

It is best to link the discussion of 'saving energy' to energy dissipation. Using 'energy saving' devices actually means that less fuel is needed to achieve the same end. Less energy is dissipated.

There are good resources for making simple estimates of, for example, the rate of energy loss through insulated and non-insulated roofs. Also useful would be comparisons of the energy needed to heat water for a bath or a shower.

Electricity is the one case where quantities are known by common knowledge through powers of appliances. And calculations are easy, energy transferred = power x time.

Power
appears in the relation P=VI P=I^2R P=V^2/R ΔQ=PΔt
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