p1 Flashcards
(39 cards)
Why can you feel thermal energy from the sun even though it is 150million km away in space?
The thermal energy travels through space as inferred radiation.
explain why putting a lid on a cup of coffee keeps the coffee warmer for longer.
the lid reduces heat loss by convection
suggest why satellites and spacecraft are often covered by sheets of shiny metal foil.
shiny surfaces are poor absorbers and emitters of thermal energy. the shiny foil helps to stop the satellite or the spacecraft getting too hot or too cold
What is wasted energy?
energy that is not usefully transferred or transformed
what happens when energy is eventually transferred to it’s surroundings.
the surroundings warm up and the energy becomes spread out to thinly to b used.
the efficiency of a coal fired power station is?
0.35
how much electrical energy is produced from coal contain 100mg of chemical energy?
35mg
what is the unit of power?
watts
what is the national grid?
the network of cables that transfer electricity for the power stations to the consumers.
explain why electricity is transferred from power stations to consumers at high voltages?
higher voltages reduce the current in the cables, which reduces energy losses from them
describe how transformers are used in the national grid
step up transformers increase the voltage from the power stations for transmission in the cables.
step down trans…. reduce the voltage to safer levels for distribution to the consumers
name 3 fossil fuels
oil
coal
natural gas
2 nuclear fuels
uranium
plutonium.
explain how thermal energy is used to produce electricity in a power station.
thermal energy release from the fuel is used to boil water.
the steam drives the turbine.
connected to a generator
which turns to generate electricity.
suggest why the efficiency of power stations is quite low
there a several energy transfer and transformation steps, and each of these will produce waste energy.
outline 3 ways that the energy in moving water can b used to generate electricity
wave machines use the rise and fall of water because of waves.
tidal barrages use the kinetic energy in moving water as the tide changes.
hydroelectric power schemes use the kinetic energy from water stored in dams to tun electricity generators
why are solar cells used to supply electricity to satellites
too high up for cables
no night or cloud in space
cells should supply electricity constantly unless the satelit goes into the earths shadow
explain why geothermal energy is sometimes described as only partly renewable
if the thermal NRG is extracted too quickly the rock will b too cold to b useful
extra electricity is needed at peak times of the day. suggest why oil fired and gas fired power stations usually provide this electricity.
they can b started up quickly but their fuel is expensive.
base load electricity is generated all the time, whatever the demand on the national grid
suggest why nuclear power stations and coal fired power stations usually provide this electricity.
they take along time to start but their fuel is cheap.
exaplain why electricity is supplied to the national grid from many different types of power station, rather than just one tyoe
the advantages of each type of power station can b exploited and their disadvantages overcome
which type of electromagnetic radiation has the higher frequency?
ultra violet?
or
infrared?
ultra violet
how do our bodies detect infrared radiation if we cannot see it?
we feel it as heat
outline how a microwave over works.
water, fats and sugars in food is easily absorb microwaves. the molecules vibrate more vigorously and the food heat up.
