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energy Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

conservation of energy

A

energy is never createdor destroted , only ever transferred between different forms and objects

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2
Q

what are 8 energy stores

A

thermal
gravitational potential
elastic
magnetic
kinetic
nuclear
chemical
electrostatic

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3
Q

what are 4 ways of tranferring energy from one store to another

A

mechanically
electrically
heating
radiation

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4
Q

what is closed system

A

neither matter or energy can enter or leave a closed system

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5
Q

what is a mechanical work done

A

it involves force to move an object

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6
Q

what is an electrical work done

A

when current flows

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7
Q

what does how much kinetic energy an object has depends on

A

it speed - the faster the object is moving the more kinetic energy it has
its mass - the more mass the object has the more kinetic energy it has(as long as the speed is the same)

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8
Q

what is a kinetic equation

A

E = 1/2 M V^2

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9
Q

what doe sthe gravitational force depend on

A

mass
distance between them

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10
Q

what is a gravitational field strenght for earth and moon

A

earth = 9.8N/kg
moon = 1.6N/kg

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11
Q

formula for grav. potential energy

A

E = mgh energy= mass(kg) x 9.8 x height(m)

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12
Q

what is a calculation for weight

A

mass x grav field strenght(9.8)

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13
Q

what si an internal energy

A

the total energy stored by the particles making up a substance or system
chemical potential energy stores + kinetic energy stores

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14
Q

what is tempreture

A

a measure of the average internal enrgy of a substance

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15
Q

what is a specific heat capacity

A

the amount of energy needed to raise the temp of 1kg of a substance by 1 C.
Also is energy released as a substance cools

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16
Q

what is a change in energy equation

A

change in energy = mass x temp change x SHC

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17
Q

What happens to ‘dissipated’ energy?

A

It is lost to the surroundings

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18
Q

what are 3 ways the heat is transferred

A

in solids = conduction
fluids = convection
thought empty space = radiation

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19
Q

how does the conduction works

A

vibrating particles transfer energy to neighbouring particles

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20
Q

what is thermal conducticity

A

how well object transfer energy by conduction
metals = hihg conductivity
fluid = low conductivyty
plastics low conductivity

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21
Q

how to reduce convection

A

stop the free flow of fluids

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22
Q

difference between conduction and convection

A

in conduction only energy is transferred but in convection it is particles that move

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23
Q

how can heat energy be transferred without particles

A

it can travel thought vaccum so basically radiation

24
Q

in 4 steps how does convection works

A
  1. As a fluid is heated the particles gain kinetic energy and spread further apart.
  2. This causes the fluid to become less dense and so it will rise above any cooler fluid that hasn’t been heated (because that fluid is more dense).
  3. As the fluid cools down it will become more dense again, and so sink back down.
  4. If this process takes place in a limited space, like a container or a room, it can create a convection current.
25
Q

how to make sure your house keeps warn

A

sealed closed
- air isn’t able to pass out = or it would lose heat energy by convection
to do so you add foam seal to your window

reduce loss by convection
- heat lost directly thought solids
- window
- wall
in order to combat that add thick walls - low thermal conductivity
or cavity walls with insulating foam between them
- this creates an air gap = reduces convection

windows = double glazing = 2 layers of glass and air
gap between them so that conduction doesn’t occur

26
Q

how to reduce friction

A

you want to reduce it because a lot of friction reduces the efficency of energy transfer

you can use lumribants like oil
or make transport streamlines

27
Q

one power defenition + equation (time)

A

power is the ratae at which energy is transfered
p = e/t

28
Q

second power defenition + equation (work)

A

power is the rate at which the work is done
P= w/t

29
Q

second power defenition + equation (work)

A

power is the rate at which the work is done
P= w/t

30
Q

what is efficency

A

proportion of the energy supply taht is actually useful

31
Q

calculation for efficency

A

efficiency = useful energy output/ total energy input

32
Q

The main renewable energy resources are:

A

Wind
Solar
Geothermal
Water waves
Biofuels
Hydroelectricity
Tidal

33
Q

Which of the energy resources below is the most widely used for heating homes in the UK?

A

natural gas

34
Q

Explain the difference between renewable and non-renewable energy resources. Use an example for each.

A

A renewable energy resource is one that is being replenished as quickly as it is used. For example solar energy is renewable because new sunlight is always being generated by the sun - we don’t use it up.

A non-renewable energy resource on the other hand is one that isn’t being replenished and so has a limited supply. For example fossil fuels like coal are non-renewable because they’re not being replenished and at some point coal could run out.

35
Q

what are fossil fuels

A

A fossil fuel is a hydrocarbon-containing material formed naturally in the earth’s crust from the remains of dead plants and animals.

36
Q

pros of fossil fuels

A

1Relatively cheap
2Can be used in any conditions (e.g. don’t require wind or sunshine to work)
3Much of our current infrastructure is designed to run using fossil fuels (e.g. most of our cars use petrol or diesel which are both made from crude oil)

37
Q

cons for fossil fuels

A

They’re a limited resource so will run out one day
2They produce carbon dioxide when burned, which is a greenhouse gas and contributes to global warming
3They sometimes produce toxic gases when burned - such as sulfur dioxide and carbon monoxide

38
Q

pros of nuclear energy

A

Nuclear fuels do not produce any pollutants like sulfur dioxide, or greenhouse gases like carbon dioxide

2Can be used in any conditions (e.g. nuclear power doesn’t depend on environmental forces like sunshine or wind)

3Although nuclear fuel (like uranium) is a limited resource, it is very unlikely to run out for a very long time

39
Q

cons of nuclear enrgy

A

Nuclear fuels (like uranium) are technically a finite resource (although nuclear power stations only use very tiny amounts so it won’t run out any time soon)
2Nuclear power stations produce radioactive waste, which remains harmful for thousands of years and so must be stored very carefully
3It is quite expensive
4If there is a problem at the power station, there is a very small chance of a nuclear meltdown which could release large amounts of radioactive material into the environment

40
Q

pros of solar

A
  • low running costs
  • don’t damage the enviroment
  • cheaper every day
41
Q

cons of solar and wind

A
  • high upfront cost
  • making them produces pollutants
  • dependant on weather
  • now way to increase supply in times of peak demnad
  • takes up lots of space
42
Q

pros of geothermal energy

A
  • installing only damages enviroment slightly
  • running it doen’t produce any pollution
  • renewable
  • reliable over long periods
43
Q

cons of geothermal energy

A
  • power plants can be expensive to build
  • only use the source in certain areas
44
Q

How geothermal power stations work

A

In regions with lots of volcanic activity, the ground is naturally very hot.
So when we pump cold water down into the ground it will be heated by the hot rocks.
If we pump this hot water back up to the surface we can use it to heat our homes.
Alternatively, we let it heat up so much that it evaporates into steam.
The steam can then be used to turn a turbine, which in turn can drive a generator to produce electricity.

45
Q

what are boifuels

A

fuel thta’s made from recently living organisms

46
Q

why are biofuels carbon netral

A

because in their lifetime plants collect Co2 and when you burn biofuel it realese CO2 so there is no overall vhange

47
Q

pros of biofuels

A

easy to transport
cheap to make
wecan benefit from them without building new cars
a renewableresource

48
Q

cons of biofuels

A
  • neeed somewhere to plant all these splants
  • release loads of Co2
    cutting down forest
  • requires energy for harvesting processing and transporting
49
Q

In theory biofuels should be carbon neutral, but in reality they are not.
Why is this?

A

In order to grow the biofuels, we often have to clear land by cutting down trees. This means the trees can no longer photosynthesise and absorb CO2 themselves, and will also release large amounts of CO2 if burned.
In addition, it usually requires a lot of energy to harvest, process, and transport the biofuels, which itself will produce a lot of CO2

50
Q

Hydroelectric dams

A

As water flows downhill (e.g. from mountains), a hydroelectric dam will trap the water in a man made lake, which is also known as a reservoir.
Then whenever water is released through the dam, it spins turbines which are connected to generators, and so produce electricity.
The water can then return to the river on the downstream side of the dam.

51
Q

tidal energy

A

Tidal barrages work in a similar way to hydroelectric dams. However, instead of damming water that’s flowed down from upstream like a conventional dam, a tidal barrage allows water to flow into a bay or river during high tide, and then releases that water during low tide.

52
Q

What are the advantage(s) of hydroelectric dams?

A

Higher electricity demands can be met by increasing water flow
They are a source of renewable energy

53
Q

What are the disadvantage(s) of hydroelectric dams and tidal barrages?

A

Upfront building costs are quite high

They can flood land upstream

54
Q

Wave Power pros

A

It is a renewable energy resource and there are no fuel costs
No harmful polluting gases are produced

55
Q

wave power cons

A

It is difficult to scale up the designs for wave machines to produce large amounts of electricity
Having many wave machines can negatively affect wildlife

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