Topic 1 - Energy Flashcards
1
Q
What are the four ways energy can be transferred
A
mechanically, electrically, by heating or radiation
2
Q
What is a system
A
A single object or group of objects that you are interested in
3
Q
What happens when a system changes
A
Energy is transferred either
-Into or away from the system
-Between different objects in the system
-Or between different types of energy stores
4
Q
What is a closed system
A
A system where neither matter or energy can enter or leave. The net change in the total energy of a closed system is always 0.
5
Q
Give an example of energy stores transferring from a kettle to water when the object is water
A
Water is the store so as the kettle heats up the water using its heating element it transfers energy into the waters thermal store, causing the temperature of the water to rise
6
Q
Give an example of energy stores transferring from a kettle to water when the kettle and water are a two object system
A
Energy is transferred electrically to the thermal energy store of the kettles heating element which transfers energy by heating to the waters thermal energy store
7
Q
What is work done
A
Energy transferred
8
Q
When can work be done?
A
-When current flows (work is done against resistance in a circuit)
-By a force moving an object
9
Q
Outline the work done when throwing a ball upwards
A
It causes a transfer from the chemical energy store of the persons arm to the kinetic energy store of the ball and the arm
10
Q
Outline the work done between a car brakes and wheels as the car slows down
A
The friction between the brakes and wheels causes an energy transfer from the wheels kinetic energy stores to the thermal energy store of the surroundings
11
Q
How do falling objects transfer energy
A
When something is dropped from a height it’s accelerated by gravity and the gravitational force does work
As it falls energy from the objects gravitational potential energy is transferred to its kinetic energy store
12
Q
What happens when there is a falling object and there’s no air resistance
A
Energy lost from the g.p.e store = energy gained in the kinetic energy store
13
Q
What does air resistance cause to energy from the object falling to do
A
Causes some energy to be transferred to other energy stores (e.g. the thermal energy stores of the object and surroundings)
14
Q
What affect does speed have on energy ?
A
Anything moving has energy in it’s kinetic energy store. Energy is transferred to this store when an object speeds up and is transferred away from this store when an object slows down
15
Q
How does speed and mass affect the kinetic energy of a system
A
The greater it’s mass and the faster it’s going the more energy there will be in its kinetic energy store
16
Q
What’s the formula for kinetic energy
A
Ek = 1/5mv ²
Kinetic energy (J) = 1/2 x mass (kg) x speed ² (m/s ²)
17
Q
How does lifting an object affect its energy
A
Lifting an object in a gravitational field requires work, causing a transfer of energy to the gravitational potential energy store of the raised object. The higher the object is lifted, the more energy is transferred of this store
18
Q
What properties of an object does the amount of energy in a g.p.e store depend on
A
-Height
-Mass
-Strength of the gravitational field the object is in
19
Q
Equation for gravitational potential energy
A
Ep = m x g x h
Gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
20
Q
What affects the elastic potential energy store of an object
A
Stretching or squashing it can transfer energy to the elastic potential energy store
21
Q
What’s the equation for finding elastic potential energy
A
Ee = 1/2ke ²
Elastic potential energy (J) = 1/2 x spring constant (N/m) x extension ² (m)
22
Q
What is a specific heat capacity
A
When more energy needs to be transferred to the thermal energy store of some materials to increase their temperature than others
23
Q
How much energy do you need to warm 1kg of water by 1°C
A
4200J
24
Q
How much energy do you need to warm 1kg of mercury by 1°C
A
139J
25
What is the measure of specific heat capacity
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
26
What’s the equation that links energy transferred to specific heat capacity
ΔE = mc Δ θ
Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C) x temperature change
27
Outline the practical to investigate specific heat capacity
-You’ll need a block of the material with two holes in it for the heater and thermometer to go into
-Measure the mass of the block and wrap it in an insulating layer (e.g. thick newspaper) to recuse the energy transferred from the block to the surroundings and insert the thermometer and heater
-Measure initial temperature and set the potential difference of the power supply to 10V and turn it on and start a stopwatch
-When you turn on the power it does work on the heater, transferring energy electrically from the power supply to the heaters thermal energy store. This energy is then transferred to the material’s thermal energy store by heating, causing the materials temperature to increase
-As the block heats use thermometer to measure it’s temperature at an even time interval and make sure the current doesn’t change
-When you have enough reading turn off the power supply
-Calculate to find the materials specific heat capacity
28
For the specific heat capacity experiment what calculations do you do to find the capacity
1. Calculate the power supplied to the heater using Power = current x potential difference
2. Then calculate how much energy has been transferred to the heater at the time of each temperature reading using the formula Energy = power x time
3. Plot graph of energy transferred to thermal energy store against temperature
4. Find the gradient of the straight part of the graph ( change in temp / change in thermal energy)
5. The specific heat capacity is 1 / (gradient x mass of the block)
29
What is the conservation of energy principle
Energy can be transferred usefully, stored of dissipated but can never be created or destroyed
30
Why isn’t all energy transferred usefully into the store it should go into
Some energy is always dissipated when an energy transfer takes place
31
Why is dissipated energy sometimes called wasted energy
Because the energy is being stored in a way that isn’t useful
32
Mobile phones as source of dissipated energy
When using a mobile phone energy is usefully transferred from the chemical energy store of the battery in the phone. But some is dissipated in this transfer to the thermal store and you will feel you phone getting warmer if you use it for a long time.
33
Flask of soup and cold spoon as an example of an energy transfer in a closed system
Cold spoon is dropped into insulated flask of hot soup which is then sealed. Energy is transferred from the thermal energy store of the soup to the useless therm energy store of the spoon so the soup cools slightly. Energy transfers have occurred within the system but no energy has left the system - so the net change in energy is 0.
34
What is power
The rate of energy transfer or the rate of doing work
35
What is the equation that links power, energy transferred and time
Power = Energy transferred / time
P = E / t
36
What is the equation that links power, work done and time
Power = work done / time
37
What are the units for power
Watts (W)
38
What happens to the systems energy store when a collision between a car and stationary object takes place
The normal contact force between car and object does work. It causes energy to be transferred from the cars kinetic energy store to other energy stores (e.g. the elastic potential and thermal energy stores of the object and the car body) Some energy may be transferred away by sound waves
39
What is conduction
The process where vibrating particles transfer energy to neighbouring particles
40
What is thermal conductivity
A measure of how quickly energy is transferred through a material due. to vibrations. Materials with a high thermal conductivity transfer energy between their particles quickly.
41
How does thermal conductivity work?
-Energy is transferred to an objects thermal store by heating which is shared across the kinetic energy stores of the particles in the object.
-The particles in the part of the object being heated vibrate more and collide which causes energy to be transferred between particles’ kinetic energy stored.
-Continues throughout the object till the energy is transferred to the other side of the object and it’s then usually transferred to the thermal energy store of the surrounding
42
What is convection
Where energetic particles move away from hotter to cooler regions
43
How does convection work
-Only in liquids and gas
-Energy transferred by heating to the thermal store which is shared across the kinetic energy store of gas or liquids particles
-The particles move faster and the space between particles increases so the density of the region decreases
-The warmer and less dense region will rise above denser cooler regions which creates a convection current
44
How do radiators create convection currents
1. Energy transferred from radiator to nearby air particles by conduction
2. The air by the radiator becomes warmer and less dense
3. The warm air rises and is replaced by cooler air which is then heated by the radiator
4. The previously heated air transfers energy to the surroundings, cools become denser and sinks
5. Cycle repeats, causing a flow of air to circulate around the room
45
How does lubrication reduce frictional forces
-Can reduce friction between objects’ surfaces that are being rubbed together. Lubricants are usually liquids so they can flow easily between objects and coat them.
46
How does frictional force effect energy transfer
Whenever something move there’s usually at least one frictional force acting against it which causes some energy in the system to be dissipated. (e.g. air resistance can transfer energy from a falling object’s kinetic energy store to its thermal energy store)
47
What methods are used to prevent heat from escaping houses
-Thick walls made from a material with low thermal conductivity. The thicker the walls and the lower their thermal conductivity the slower the rate rate of energy transfer will be
-Thermal insulation
48
Give examples of how insulation is used in housing to prevent heat from escaping
-Cavity walls made up of an inner and outer wall with an air gap in the middle which reduces the amount of energy transferred by conduction through the walls. Cavity wall insulation where the gap is filled with foam can also reduce energy transfer by convection.
-Loft insulation can reduce convection currents being created in lofts
- Double-glazed windows work in the same way as cavity walls - air gap between 2 sheets of glass to prevent energy transfer by conduction through windows
-Draught excluders around doors and windows reduce energy transfers by convection
49
Outline the practical to investigate the effectiveness of materials as thermal insulators
1. Boil water in a kettle. Pour some into a sealable container to a safe level. Measure the mass of water in the container
2. Use a thermometer to measure the initial temperature of the water
3. Seal the container and leave for 5 minutes. Measure this time using a stopwatch
4. Remove the lid and measure the final temperature of the water
5. Pour away the water and allow the container to cool to room temperature
6. Repeat but wrap container in a different material once it has been sealed
7. The lower the temperature difference the better the material is as a thermal insulator
8. Also investigate the effect the thickness
50
What is the efficiency of something
The less energy that is wasted in this energy store the more efficient something is
51
How can the efficiency of something be improved
By insulating objects, lubricating them or making them more streamlined
52
What’s the equation for efficiency
Efficiency = Useful output energy transfer / Total input energy transfer
53
What is the equation for efficiency is you only know the power
Useful power output / Total power input
54
Why are electric heaters usually 100% efficient
All the energy in the electrostatic energy store is transferred to ‘useful’ thermal energy stores
55
How does hydroelectric power work
Requires the flooding of a valley by building a big dam. Water is allowed out through turbines
56
What is the negative of hydroelectric power
Big impact on the environment due to the flooding of the valley (rotting vegetation releases methane and CO2) and loss of habitat and sometimes whole villages. Reservoirs look ugly when dried up.
57
What are positives of hydroelectric power
-It can provide an immediate response to an increased demand for electricity
-No problem with reliability except in times of drought
-No fuel costs and minimal running
-Useful to generate electricity on small in remote areas
58
How and where does wave power work
Lots of small wave-powered turbines located around the coast and the turbines are connected to a generator
59
What are the negatives of wave power
-Disturb the seabed and the habitats of marine animals, spoiling the view and being s hazard to boats
-Fairly unreliable since waves tend to die out when the wind drops
60
What are the positives of wave power
-There are no fuel costs and minimal running costs
-Can be useful on small islands - not large scale
61
How do tidal barrages work
-Big dams built across river estuaries with turbines up in them and as the tide comes in it fills up the estuary and the water is then allowed out through turbines at a controlled speed
-Tides are procured by the gravitational pull of the sun and moon
62
What are the negatives of tidal barrages
-Preventing free access by boats, spoiling the view and altering the habitat of the wildlife
-Height of tides is variable so lower tides will provide less energy than bigger tides and they don’t work when the water level i’d the same either side of the barrage (4 times a day)
63
What are the positives of tidal barrages
-Tides are reliable as they happen twice a day without fail
-No fuel costs and minimal running costs
-Most suitable estuaries have the potential for generating a significant amount of energy
64
What are the three main fossil fuels
Coal, oil and natural gas
65
What are fossil fuels
Natural resources that form underground over millions of year and they are typically burnt to provide energy.
66
What are the positives and negatives of fossil fuels
P : They are reliable
N : They will all run out one day and they do damage to the environment
67
What are some renewable energy resources
The sun, wind, water waves, hydro-electricity, biofuel, tides and geothermal
68
Positives and negatives of renewable energy
P : They will never run out and don’t do as much damage as non-renewable energy
N : Don’t provide as much energy as non-renewable sources and some are unreliable as they depend on the weather
69
How are non renewable energy sources used for transport
-Petrol and diesel powered vehicles use fuel created from oil
-Coal is used in some old fashioned steam trains to boil water to produce steam
70
How are renewable energy sources used for transport
Vehicles that run on pure bio-fuels or a mix of a bio-fuel and petrol or diesel
71
How are non-renewable energy sources used for heating
-Natural gas is the most widely used fuel for heating homes in the U.K. a it is used to heat water which is then pumped into radiators throughout the home
-Coal is commonly burnt in fireplaces
-Electric heaters which use electricity generated from non-renewable energy resources
72
How are renewable energy sources used for heating
-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
73
How is wind power used as an energy source
-Lots of wind turbines put up in exposed places like on moors or round coasts
-Each turbine has a generator inside it and the rotating blades turn the generator and produce electricity
74
What are the positives of wind turbines
-No pollution
-No fuel costs and minimal running costs
-No permanent damage to the landscape
75
What are the negatives of wind turbines
-They spoil the view
-Can be very noisy
-Not reliable as the wind stops or can be too strong
76
How do solar cells generate electricity and where are they best used
-Directly from sunlight
-Best source of energy to charge batteries in calculators and watches which don’t use much electricity
77
What are the positives and negatives of solar cells
P : There’s no pollution, in sunny countries solar power is a very reliable source of energy - but only in the day. Solar cells can be efficient in cloudy countries such as Britain. Energy is free and running costs are almost nil
N : Small scale, initial cost is high and you can’t increase power output when there is extra demand
78
Where is geothermal power possible
-Volcanic areas or where hot rocks lie quite near to the surface. The source of much of the energy is the slow decay of various radioactive, including uranium, deep inside earth.
79
What are the positives of geothermal power
-Free energy that’s reliable and does little damage to the environment
-Can be used to generate electricity or heat buildings directly
80
What are the negatives of geothermal power
There aren’t many suitable locations for power plants, and that the cost of building a power plant is often high compared to the amount of energy it produces
81
How is biofuel used as a source of energy
Created from either plant products or animal faeces. They can be solid, liquid and gas and can be burnt to produce electricity or run cars in the same way as fossil fuels.
82
Positives of biofuels
They are supposedly carbon neutral and are fairly reliable as crops take a relatively short time to grow and different crops can be grown all year round. Continuously produced and stored for when they’re needed.
83
Negative of biofuel
-Cannot respond to immediate energy demands
-To refine bio-fuels is very high and some worry that growing crops specifically for bio-fuels will mean there isn’t enough space or water to meet the demands for crops they are grown for food
-Large areas of forest have been cleared to make room resulting in species losing their habitats
84
What causes the release of sulphur dioxide and what in turn does this cause
Burning coal and oil releases sulfur dioxide which causes acid rain which can be harmful to trees and soils and can have far-reaching effects in ecosystems
85
How can acid rain be reduced
By taking the sulfur out before the fuel is burnt
86
What is the problem with nuclear power
It’s clean but nuclear waste is very dangerous and difficult to dispose of.
Always carries major risk like the Fukushima disaster in Japan
87
What is the problem with nuclear fuel
It is relatively cheap but the overall cost is high due to the cost of the power plant and final decommissioning
88
Why have the government began to take action against overuse of non-renewable energy
Pressure from other countries and the public has meant targets for using renewable resources are being put in place. This put pressure on energy providers to build new power plants that use renewable resources to ensure they don’t lose business and money.
89
How have car companies responded to the change in attitude towards the environment
Electric cars and hybrids are already on the market and their popularity is increasing
90
Why has energy use in the U.K. been slowly decreasing since the beginning of the 21st century
We are better at making appliances more efficient and are more careful with energy use in our homes
91
Why do power plants limit the use of renewability
-Costs money so some energy providers are reluctant
-The cost of switching to renewable power will have to be paid, either by customers in their bills, or through government and taxes
-Some people don’t want or can’t afford to pay extra
92
Why does power plants not being ethical limit use of renewable
-There are arguments for where to put power plants
-Many people don’t want to be put next to a wind farm for example
93
Why does reliability limit the use of renewables
-Wind power for examples is not reliable
-Other cannot increase their power output on demand
-This means either using a combination of power plants (expensive) or researching ways to improve reliability
94
What is the problem with researching reliability of renewables
-Takes time and money
-May be years before improvements are made even with funding
95
Why are personal changes for people limiting the use of renewable
-Can be expensive
-Hybrid cars are generally more expensive than equivalent petrol cars
-Solar panels for home are quite pricey
