1
Q
Energy is… Instead it’s
A
Energy is never used up. Instead it’s transferred between different energy stores and different objects
2
Q
What are the different energy stores (8)
A
- Thermal
- Kinetic
- gravitational potential
- elastic potential
- chemical
- magnetic
- electrostatic
3
Q
How is energy transferred mechanically
A
by a force doing work
4
Q
What is a system
A
A system is a single object (e.g. air in piston) or a group of objects (e.g. two colliding vehicles) that you’re interested in
5
Q
What happens when a system changes
A
- Energy is transferred
- It can be transferred into or away from the system
6
Q
What is a closed system
A
- Closed systems are systems where neither matter nor energy can enter or leave
- the net change in the total energy of a closed system is always 0
7
Q
Explain energy transfer of eater boiling in a kettle
A
- the water is the system
- energy is transferred to the water from the kettle by heating into the water’s thermal energy store
- causing energy to rise
8
Q
What is work done
A
- the energy transferred
- it can be done when current flows (work is done against resistance in a circuit) or by a force moving an object
9
Q
Describe the energy transfer of a person throwing a ball upwards
A
- initial force exerted by a person to throw a ball upwards
- energy transfer from chemical energy store of person’s arm to the kinetic energy store of the ball and arm
10
Q
Do falling objects transfer energy
A
- yes
- the object is accelerated by gravity
- so gravitational force does work
- as it falls, energy from the g.p.e store is transferred to its kinetic energy store
- energy lost from the g.p.e store = energy gained in the kinetic energy store
11
Q
Kinetic energy store is found in anything that is…
A
Moving
12
Q
How is energy transferred in a kinetic energy store
A
- it is transferred to this store when an object speeds up
- it is transferred away from this store when an object slows down
- the energy is dependent on the object’s mass and speed
13
Q
Formula for kinetic energy
A
Kinetic energy = 0.5 x mass x speed^2
14
Q
What is the amount of energy in g.p.e. Stores dependent on
A
- object’s mass
- object’s height
- strength of gravitational field the object is in
15
Q
How is energy transferred to g.p.e. Store
A
By lifting an object in a gravitational field, because it require work, it means there’s a transfer of energy to the g.p.e. Store of the raised object.
16
Q
Formula for g.p.e.
A
Gravitational potential energy (J) = Mass x gravitational field strength x height
17
Q
How do you transfer energy to elastic potential energy stores
A
- stretching or squashing an object can transfer energy to its elastic potential energy store
- so long as the limit of proportionality has not been exceeded
18
Q
What is the equation for the elastic potential energy
A
Elastic potential energy = 0.5 x spring constant (N/m) x extension^2 (m)
19
Q
What is specific heat capacity
A
The amount of energy needed to raise the temp of 1 kg of a substance by 1’C
20
Q
Explain specific heat capacity
A
- some objects thermal energy stores require more energy than others
- because they have different specific heat capacities
- they need lots of energy to heat up - they transfer lots when they cool down
- The measure of how much energy a substance can store is called its specific heat capacity
21
Q
What is the specific heat capacity equation
A
Change in thermal energy = mass x specific heat capacity (J/Kg’C) x temperature change
22
Q
What is the conservation of energy principle
A
Energy can be transferred useful, stored or dissipated, but can never be created or destroyed
23
Q
What is wasted energy
A
The energy that is dissipated and isn’t useful (e.g. thermal energy when you use your phone)
24
Q
What are the 4 ways energy can be transferred
A
- Mechanically - by a force
- electrically - by an electrical current
- radiation - light waves or sound waves
- by heating - By conduction, convection or radiation
25
What is power
- The rate of energy transfer
- measured in watts
- 1 watt = 1 joule of energy transferred per second
26
How to you calculate power
Power = energy transferred / time. Or Power = Work done / time
27
WHat is conduction
- Conduction is the process where vibrating particles transfer energy to neighbouring particles
- The particles in the part of the object being heated vibrate more and collide with each other. These collisions cause energy to be transferred between particles’ kinetic energy stores. This is conduction
- The process continues throughout the object until the energy is transferred to the other side of the object, then dissipated to environment
28
WHat is Convection
- Convection is where energetic particles move away from hotter to cooler regions
- Convection can happen in gases and liquids. Energy is transfered by heating the thermal energy store of the liquid or gas.
- When heat is increased, the particles move faster and the space between individual particles increases.
- causing the density of the region being heated to decrease
- because liquids and gases can flow, the warmer and less dense the region will rise above denser, cooler regions.
- So energetic particles move away from hotter to cooler regions - This is convection.
29
How do you reduce unwanted energy transfers
- lubrication (it reduces frictional forces)
- Insulation (it reduces the rate of energy transfer by heating)
30
How does lubrication work
- whenever something moves, there’s usually at least on frictional force acting against it. This causes some energy in the system to be dissipated
- lubricants can be used to reduce the friction between the objects’ surfaces when they move
- They are usually liquids (like oil), so they can flow easily between objects and coat them
31
How does insulation work
They energy loss through heating. This can be done by:
- having thick walls that are made from a material with a low thermal conductivity. The thicker the walls and the lower their thermal conductivity, the slower the rate of energy transfer will be (so buildings will cool more slowly)
- Use thermal insulation
32
Give examples of thermal insulation
- Cavity walls
- Loft insulation
- Double glazed windows
- Draught excluders
33
What are the three ways you can increase efficiency
- insulate
- lubricate
- make object more streamlined
34
how to work out efficiency
Efficiency = useful output energy transfer (or total power out put) / total input energy transfer (total power input)
35
Explain the efficiency of electric heaters
- 100% efficient
- because all the energy in the electrostatic energy store is transferred to “useful” thermal energy stores
36
Explain what is meant by Non-renewable energy and give examples
- they will ‘run out’ one day, they do damage to the environment, however they are reliable
- Coal
- Oil
- (natural) Gas
37
Explain what is meant by renewable energy and give examples
- They will never run out of energy, can be renewed, don’t do as bad damage to environment as non renewable
- some can be unreliable as they are dependent on weather
- solar
- wind
-water waves
- hydro-electricity
- bio-fuel
-Tides
- Geothermal
38
How are energy resources used for transport
NON RENEWABLE
- petrol and diesel created from oil to be used by cars
- coal from old-fashioned steam trains to boil water to produce steam
RENEWABLE
- vehicles that run on pure bio-fuels or a mix of a bio fuel and petrol or diesel (only biofuel bit is renewable tho)
39
How are energy resources used for heating
NON RENEWABLE
- Natural gas is used to heat homes: it heats water which is then pumped into radiators in homes
- Coal is commonly burnt in fireplaces
- Electric heaters use electricity generated from non-renewable energy resources
RENEWABLE
- geothermal heat pumps use 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
40
Advantages of Wind power
- no harmful chemical by-products
- renewable source of energy
- source of energy is free
41
Disadvantages of wind power
- source of energy is dependent on weather, could be a day without wind
- low energy density
- bad aesthetic look, for some
- can be noisy
42
How do wind turbines work?
The force of the wind turns the turbine, which powers a generator and produces free, clean electricity. However, the amount produced is small.
43
Advantages of solar power
- no harmful chemical by-products
- renewable source of energy
- free source of energy
44
Disadvantages of Solar power
- can only be utilized during the day
- source of energy is unreliable, dependent on weather - could be a cloudy day
- low energy density - need a large area would be needed for a significant amount of energy
45
How does solar power work
- Solar cells use energy from sun to generate electricity
46
advantages of geothermal power
- It can heat buildings directly
- Free, Renewable, no real environmental problems
47
disadvantages of geothermal energy
-ecosystem disturbance
-replenishment rates of ground heat
-high start up costs
-geographic limitations
48
How does geothermal power work?
- Water is pumped down to hot rocks
- steam is forced back up due to Pressure
- steam turns turbine which drives Generator
49
Advantages of Hydro-electric power
- It can provide an immediate response to an increased demand
- no fuel costs
- minimal running costs
- no pollution(as such)
50
Disadvantages of hydroelectric power
- can only be utilized in areas with water
- environmental effects on marine animals
- construction of dam will involve land being buried underwater
51
How does hydro-electric power work?
Hydro-electric power transfers energy from the kinetic store of falling water using turbines and generators.
52
Advantages of wave power
- No pollution and renewable
- No fuel costs and minimal running costs
- Very useful on small islands
53
Disadvantages of wave power
- Spoiling the view
- A hazard to boats
- Fairly unreliable as waves die out when wind drops
- Initial costs are high
- Unlikely to provide energy at a large scale
54
How does wave power work?
-Waves come to shore and provide up and down motion
-Directly drives a turbine
-Which drives a generator
55
Advantages of tidal barrages
- No pollution and renewable
- Tides are pretty reliable
- Minimal running costs
56
Disadvantages of tidal barrages
- Preventing free access by boats
- Spoiling the view
- Altering the habitat of the wildlife
- Initial costs are moderately high
57
How do tidal barrages work?
- As the tide comes in it fills up the estuary
- the water is then let out through turbines at a controlled speed to generate electricity
58
What are bio-fuels?
Renewable energy resources created from either plant products or animal dung
59
How do Bio-fuels work?
They are organic waste or living matter and are burnt to power a turbine, which turns a generator.
60
Advantages of biofuels
- Cheap,
- readily available,
- if crops/trees are replanted it can be a renewable and sustainable source
61
disadvantages of biofuels
-increased car emissions and smog
-competes with food for cropland
-clearing natural areas for plantations reduces biodiversity and increases atmospheric CO2 levels
62
Advantages of non renewable energy
- they are abundant and affordable.
- Non-renewable energy is cost effective and easier to product and use.
63
Disadvantages of non renewable energy
- Slowly running out
- release greenhouse gases into the atmosphere
- coal and oil release sulphur dioxide which causes acid rain
- coal mining can destroy views
- oil spillages cause environmental problems
- nuclear waste is dangerous and difficult to dispose of
- nuclear power is expensive due to power plant and decommissioning
- nuclear power poses high disaster risk
64
What is thermal conductivity
Thermal conductivity is a measure of how quickly energy is transferred through a material in this way.
65
How do cavity walls work
- made of inner and outer wall with an air gap in between.
- The air gap reduces the energy lost when transferred by conduction through the walls.
- Sometimes the air gaps are filled with foam, also reducing energy transfer by convection in the wall cavity
66
Describe how loft insulation works
- fibre glass wool is laid across loft floor or ceiling.
- It is good because it has pockets of trapped air.
- This reduces energy loss by conduction and also prevents convection currents
67
How does double glazed windows work
- works the same way as cavity walls
- they have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows
68
How do draught excluders work
Built around doors and windows reduce energy transfers by convection
Physics GCSE
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