p8 ocr gateway

fossil fuels

non renewable source

combustion produces thermal energy witch heats water which creates steam to turn turbine

nuclear fuels

non renewable source

fission produces thermal energy which is used to turn turbines

bio fuels

renewable source

combustion for thermal energy to turn turbines

wind

renewable

directly turns turbines which generate electricity

hydroelectricity

renewable

water moving from a height with gpe directly turns a turbine which generates electricity

tidal

renewable source

wave action directly turns turbines in tidal barrage

solar

renewable

solar cells directly produce electricity from the suns energy

trends in the use of energy

energy consumption was very low before the 1850s. in the 1800 there was a sharp rise in coal use due to the industrial revolution.

extraction of crude oil and fossil fuels also saw a rise in petrol and natural gas from the 1900.

nuclear power has risen from late 1900

only very recently has renewable energy been used. most commonly hydroelectric and wind.

the national grid

electrical power is transferred at high voltages from power stations for domestic use via overhead power lines. these high voltages are reduces to safer lower voltages when reaching each settlement for domestic use

step up transformers

are used to increase the potential difference from power stations and power lines. this reduces the current and therefore reduces the energy lost to heat in these lines

step down transformers

used to decrease potential difference from power lines to domestic use. This increases the current to a usable level.

power

the same enters a transformer leaves a transformer. as potential difference increase in a step up transformer, current is decreased, since power loss is due to p=l²r

reducing the current reduces energy loss. Therefore transformers are effective at reducing the amount of power lost.

mains electricity

mains electricity is alternating at 50Hz and 230v. AC varies from a positive maximum and negative minimum and constantly changes

direct electricity

is at a constant fixed positive amount and is the type of supply provided by batteries and cells.

live wire

brown in colour

carries voltage from mains to appliance

this may be dangerous even if the mains circuit is off, as current may be flowing through it.

neutral wire

blue in colour

completes the circuit

earth wire

green and yellow striped

safety wire to stop the appliance from becoming live.

is connected to the earth and the casing

if the live wire touches the metal casing of the appliance, it will become live.

the earth wire is connected to the metal casing and its low resistance will mean that the current will go from the casing through the earth wire and to the ground.

red shift

light appears red shifted from galaxies which are moving away from the earth. the change with distance of each galaxies speed is evident of an expanding universe.

the wavelength appears to get larger, frequency appears to decrease, as each time a wavelength is emitted, the source is further away.

cosmic microwave background radiation

when the universe was very young everything was very hot, and would have emitted lots of short-wavelength radiation.

as the universe expanded over time,the wavelength of this radiation would’ve been stretched to become microwaves.

this background radiation is present wherever you point a telescope in the sky, which proves that the hot young universe has cooled and expanded ever since

lifecycle of a star