Physics Unit 1

Questão	Responda
What does conservation of energy mean?	Energy cannot be created or destroyed, only transformed or transferred.
Describe the energy transfer that takes place in a microphone	Electrical energy is converted into sound (useful) and heat (waste)
Describe the energy transfer that takes place in a laptop	Chemical energy is transferred to light (useful), sound (useful) and heat (waste)
A phone charger has an input energy of 5J. It wastes 1.5J as heat. Draw a Sankey diagram to show this energy transfer.	Image: Sankey_diagram (image/png)
What is the formula for efficiency?	Efficiency = Useful output power / Total input power
What is the definition of power?	The rate of energy transferred
What is the formula for power?	Power (W) = energy (J) / time (s)
What are Kilowatt hours a unit of?	Energy
How do you work out kilowatt hours?	Kwh = kW X hours
How do you work out GPE?	Mass x gravity x height
Why does a pendulum gradually not swing as high?	Some energy is lost because it is wasted as sound and heat
What is the formula for energy?	Energy = power x time
How do you work out payback time?	Payback time (years) = cost of insulation / saving each year
How do you work out cost effectiveness?	Saving each year/cost of insulation
What is a U-value and what does a low U-value tell us?	A U-value is a measurement of the rate of heat loss through a material. The lower the U-value, the better the material is as an insulator.
In a power station what happens in the boiler?	Burning coal heats water. The water turns to steam and leaves the boiler.
In a power station what happens in the turbine?	Steam turns the turbines. The steam then leaves the turbines and is cooled in huge towers and the water can be recycled.
In a power station what happens in the generator?	The turbines drive a large magnet inside a coil. Moving the magnet generates electricity.
In a power station what happens in the transformer?	The transformer changes the voltage from 25,000V to 400,000V
What is a fuel?	A source of energy
What is oil?	Fossils of animals
What is coal?	Fossils of plants
What are some advantages of wind power?	Clean Renewable source of energy
What are some disadvantages of wind power?	Turbines look ugly and are noisy Unreliable
Advantages of water power?	Renewable Doesn't affect coastal views
What are some disadvantages of water power?	Waves can damage turbines in wave power Tidal power can only be used in places where there is a 5m difference between high and low tide
Describe wave power	Waves force the air up and the trapped air turns the turbine which turns the generator. As the wave comes down, the air comes back
Describe tidal power	A tidal power station traps each high tide behind a barrage and uses it to turn the generator to make electricity.
Describe hydroelectric power	Dam. Dam wall is much thicker at the bottom than the top because the pressure of the water increases with depth. Falling water turns the turbine.
Describe geothermal energy	Geothermal energy harnesses thermal energy stored within the Earth. Cold water goes down, gets heated up by radioactive rock, the comes back up as steam and turns the turbine.
What causes acid rain?	Sulfur dioxide, produced when sulfur is burned. Sulfur occurs due to impurities in fuels.
What does the first step down transformer do?	Reduces voltage from 400,000V to 25,000V
What does the second step down transformer do?	Reduces voltage from 25,000V to 230/240V
Does a step up transformer have more coils on the output side?	Yes
What is the order of start up times for power stations from shortest to longest?	Natural gas, oil, coal, nuclear
Energy can be dissipated	True
What is a kilowatt hour sometimes called?	A unit
Why does voltage need to be increased before electricity goes down power cables?	Increasing the voltage reduces the current required and this reduces the heat energy losses form the cables
What is carbon capture?	Carbon capture is the capture of the carbon dioxide released by burning fossil fuels
Image: Nuclear (image/png)	Image: Nuclear (image/png)
Name two radioactive fuels	Uranium Plutonium

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	Criado por Melissa Quail mais de 10 anos atrás