P3 Revision Notes

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P3 –

Making decisions –

People may disagree

about which technologies should be allowed. Some decisions may be based on

the best outcome for the greatest number of people or a moral sense of

right and wrong.

The benefits of science-based

technologies must be weighed against their costs.

Human activity may

have unintended impact on the environment. Scientists may be able to

suggest ways of reducing this impact.

The development of

science-based technology is often subject to government regulation.

Electricity –

·

Many power

stations use a primary energy source to boil water into high pressure steam.

The steam passes through turbines forcing them to spin round. The turbines spin

the magnets inside generators so that a voltage appears across the coil inside.

Increasing the rate of energy transfer from the primary source increases the

current in the generator.

·

The

efficiency of a power station is the ratio of its useful output to the total

energy input.

·

Electricity

can transfer energy easily from one place to another along the National Grid.

Domestic electricity consumption is measured in units of kilowatt-hours (kWh).

·

Electricity

is a secondary energy source made from primary energy sources such as fossil

fuels, uranium, wind, water and sun.

·

Electric

current transfers energy from a power supply to an electric appliance.

·

Energy transferred = power x time.

·

The power of

an appliance is the energy transfer per second.

·

Power = voltage x current.

Nuclear power –

·

Nuclear

power stations produce radioactive waste which emits harmful ionising

radiation.

·

Nuclear

power stations are expensive to build but their fuels do not emit carbon

dioxide.

·

Exposure by

irradiation can be limited by shielding and keeping away from the source of

radiation.

·

Exposure by

contamination is often more dangerous because the radioactive material has been

incorporated into the body so cannot be removed.

·

Exposure of

people to ionising radiation can result in cancer.

Renewables –

·

Solar cells

produce electricity directly from sunlight without producing carbon dioxide.

Solar power requires a lot of land and, like wind power, is very weather

dependent.

·

Hydroelectricity

has a large environmental impact as well as being expensive to build.

·

Geothermal

power can only happen in places where rocks are hot near the Earth’s surface.

·

Wind

turbines are spun directly by the wind. They do not produce carbon dioxide but

have a visual impact.

Carbon fuels –

·

Biofuels,

e.g. wood, plant oils, are renewable and result in no net change of carbon

dioxide in the atmosphere.

·

Fossil fuel

power stations can easily make large amounts of electricity, but they are

expensive to build.

·

Coil, oil

and gas produce carbon dioxide when they are burnt to make electricity.

·

Some fossil

fuels will last longer than others, but they will run out eventually.