Conservation of energy and power Flashcards Preview

Physics > Conservation of energy and power > Flashcards

Flashcards in Conservation of energy and power Deck (56):
1

Can energy be destroyed?

NO ENERGY CAN NEVER BE DESTROYED

2

If energy cannot be destroyed, what is the principle/rule of energy?

Energy can be transferred usefully, stored or dissapated but can never be destroyed or created

3

When you transfer energy is all of it transffered usefully?

No, some energy is always dissipated when energy transfer takes place, called 'wasted energy'

4

If a cold spoon is dropped into a insulated flask of hot soup, which is then sealed what happens in terms of energy in this closed system?

energy is transferred from the theermal energy store of the soup to the useless thermal energy store of the spoon, causing the soup to cool down slightly, energy transfers have happened within the system but no energy has left the system so the net change is 0

5

What is power?

Power is the rate of 'doing work' or energy trasnfer

6

How do you measure power?

Power is measured in watts. One watt = 1 joule of energy transferred per second

7

What are the equation for power in terms of energy?


Energy Transferred (Joules)
Power= ----------------------------------------
Time (Seconds)

Work done (Joules)
Power=---------------------------------------------
Time (Seconds)

8

How can we reduce wasted energy?

Lubricating frictional forces
Insulating objects

9

How does lubricating minimise wasted energy transfer?

They reduce friction between two moving friction forces, which reduces the amount of energy dissipated

10

What is thermal conductivity?

Is a measure of how quickly energy is transferred through a material via vibration and collision with other particles. Materials with a high thermal conductivity transfer energy between their particles at a faster rate

11

What happens in terms of particles and density when conduction occurs?

the particles are free to move and are moving faster which means the space between the particles increases, which means the density of the region to decrease

12

How does insulation minimise wasted energy transfer?

It reduces the rates of convection and conduction inside the thing your insulating

13

What is convection heating?

when liquids and gases flow the warmer and less dense part of the gas or liquid will rise to the top while the more dense and cooler part sinks to the bottom, so the energetic particles move away from hotter regions to cooler regions

14

What is efficiency

How good a device is at making sure as much energy input is transferred into a useful energy store not a waste one

15

How do you make a device more efficient

Lubricating
Insulating
Streamlining

16

What is the equation for efficiency?


Useful output energy(or power) transfer
Efficiency=----------------------------------------------------------
Total input energy(or power) transfer

17

Can a device be 100% efficient and if there is what is it?

Only device 100% efficient is an electric heater, as all energy being transferred goes to the thermal energy store anyway which is what that devices purpose is. Most devices waste energy store is heat (e.g. a computer)

18

Where does all energy eventually end up?

THERMAL ENERGY STORE

19

Define what a non-renewable energy source is in terms of science?

Are fossil fuels and nuclear fuel (uranium and plutonium)
They are fuel sources that will eventually run out, and cause harm to the environment

20

Define what a renewable energy source is

They are energy sources that will never run out, and they can be replenished as it is being used

21

What are the features of a non renewable energy source

They will run out some day
They do damage to the environment
they are all naturally occurring

22

What are the features of a renewable energy source

They will never run out as the energy can be renewed as it is used
They cause visual and noise pollution and don't release poisonous gases.
They don't provide as much energy as non renewable
Sometimes they can be unreliable as they depend on the weather

23

Name some non renewable energy sources

Coal
Oil
Gas

24

Name some renewable energy sources

wind
Biofuel
water waves
Hydro-electricity
The sun(solar power)
Tides
Geothermal

25

How are non renewable energy sources used in transport?

Petrol and Diesel powered vehicles(most cars)
Coal in old fashioned steam trains

26

How are renewable energy sources used in transport?

Vehicles that can run on pure biofuel or a mix of it and petrol/diesel

27

How are non renewable energy sources used for heating your home

Natural gas is the most widely used fuel for heating homes in the UK. The gas is used to heat water, which is then pumped into radiators throughout the house

Coal is commonly burnt in fireplaces

Electric heaters which use electricity from non renewable energy sources

28

How are renewable energy sources used for heating your home

A geothermal heat pump uses geothermal energy resources to heat buildings

Solar water heaters work by using the sun to heat water which is then pumped into radiators in the building

Burning bio-fuel or using electricity generated from renewable resources can also be used for heating

29

How does the wind generate energy

Lots of wind turbines are put up in exposed places such as coasts and moors

When the wind catches the turbine it spins the turbine and turns a generator

30

What are the benefits to wind power

There is lots of wind
There's no pollution created
Minimal running costs
No permanent damage to the landscape

31

What are the disadvantages to wind power?

Very noisy
Spoil the landscape while they are there
turbines stop making power when the wind stops, cant increase the supply
initial costs are quite high

32

How does solar power generate electricity?

The solar cells generate an electric current when the sun hits them, best used for small appliances that don't require much power like watches or calculators

33

What are the benefits to solar power on a large scale?

Used in deserts or remote places where there's not much option for alternatives, makes use of the land

There is no pollution

it is a very reliable source as you know there will always be sun during the day, even if its cloudy its still effective

running costs are almost nothing

34

What are the disadvantages of solar power

You cant increase the power output when there is extra demand

High initial cost

usually can be used on a relatively small scale

35

How does geothermal power generate electricity

possible in volcanic areas or where hot rocks lie quite near to the surface. Uses heat to heat up water and as it rises it turns a turbine

36

What are the benefits of geothermal power?

Free energy

Reliable

Little damage to the environment

can heat buildings directly

37

What are the disadvantages to geothermal power

the cost of setting up a geothermal power station are high compared to the amount of energy it makes

hard to find suitable locations

38

How does hydro-electric power work?

Usually stations are built on a reservoir or a fast flowing river and as water flows through it, it would generate electricity

39

What are the advantages of hydro electric power?

It generates no pollution

can immediately cope with increase in the demand by letting more water flow

Reliable except if there's a drought

Minimal running costs

can be used on the small scale and in remote areas

40

What are the main disadvantages of hydro-electric power?

Large impact on destruction of habitats and the river quality

Valley gets flooded destroying homes

look ugly

41

what is wave power?

lots of small wave powered turbines are located around the coast, and they are connected to a turbine

42

What are the benefits to wave power?

there is no pollution

no fuel costs

minimal running costs

useful on the smaller scale

43

What are the disadvantages to wave power

unreliable

disturb wildlife and their habitats

spoil views and are hazardous to boats

cant be used on the large scale

44

What is tidal power?

it is when there is a tidal barrage built across a river estuary, as the tide comes In it fills up the estuary and it flows through at a controlled speed and turns a turbine which turns a generator

45

What are the benefits of tidal power?

No pollution

pretty reliable

no fuel costs

minimal running costs

can generate lots of power

46

What are the disadvantages of tidal power

Initial costs are moderately high

disturbs wildlife and destroys habitats when built

Amount of power made is variable

hard to find suitable estuaries

spoil the view

47

What is biofuel?

bio-fuels are renewable energy sources created from plants or animal faeces, they can be solid, liquid or gas and can be burnt to produce electricity and run cars in the same way fossil fuels can

48

What are the benefits to biofuel?

They are carbon neutral(only true if the rate of use same as rate of growth of plants)

reliable- as any crop can be used or any poo short time needed to grow new crops/poo

Can be stored for use

act similarly to fossil fuels

49

What are the disadvantages to biofuels?

high refining cost

demand cant be met for food also

deforestation has to happen to make space for production and growth of biofuels further hurting the environment also increase CO2 and methane emissions

cant respond to immediate energy demands

50

What are the benefits to non-renewable sources of energy?

They are very reliable, and can keep up to current demand

can be extracted as they are being used

running costs aren't expensive

low fuel extraction costs

cost effective way to produce energy

51

What are the disadvantages to non-renewable sources of energy?

CO2 released into atmosphere creating a greenhouse affect that contributes to global warming

Sulfur dioxide released which creates acid rain (can be reduced by taking out the emmisions)

Mining for the resources ruins the landscape

Oil spillage causes serious environmental problems

Nuclear power is clean but the waste is very harmful and hard to dispose of properly

Nuclear fuel is cheap (Uranium) but the overall cost is high due to the cost of the power plant and the final decommissioning

Nuclear always has the potential of having a large disaster such as Fukushima in Japan

52

What was the reason for increasing demand in energy in modern times?

Population growth and the increasing amount of appliances that rely on electricity

53

Why is our reliance on electricity decreasing?

Appliances are becoming more efficient and use energy more responsibly

Also trying to use more renewable energy sources

54

How is most of our power made today?

By non renewable sources such as, coal, gas, oil and nuclear

55

How else do we use energy apart from electricity?

fuel cars

heat

56

How is this new energy reducing attitude affected things?

More electric cars and hybrids being developed along with the infrastructure for them

Energy providers want to introduce renewables so that they don't lose business and energy

Countries make targets for change