Topic 1 - Energy Flashcards
What are the 8 energy stores that you need to know?
- Thermal energy stores
- Kineic energy stores
- Gravitational potential energy stores
- Elastic potential energy stores
- Chemical energy stores
- Magnetic energy stores
- Electrostatic energy stores
- Nuclear energy stores
Define
closed system.
a system in which neither matter nor energy can enter or leave
the net change in the total energy of a closed system is alway zero
What is the equation for
Kinetic Energy?
(involving mass, velocity and kinetic energy)
KE = 1/2(mv^2)
Kinetic Energy (J) = 1/2 (mass (kg) x speed (m/s)^2)
What is the equation for
Gravitational Potential Energy?
(involving field strength, height, mass and gpe)
GPE = mgh
GPE (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
What is the equation for
Elastic Potential Energy?
(involving spring constant, extension and epe)
EPE = 1/2 (ke^2)
EPE (J) = 1/2 (spring constant (N/m) x extension (m)^2)
Define
specific heat capacity.
the amount of energy needed to raise the temperature of 1kg of a substance by 1°C
What equation links
specific heat capacity, energy transferred, mass and temperature?
ΔE = mcΔT
Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C) x temperature change (°C)
What is the
conservation of energy principle?
energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
What is
power?
And what is it measured in?
the rate of energy transfer or the rate of doing work
it is measured in watts
1 watt = 1 joule of energy transferred per second
What equation links
energy, power and time?
P = E/t
Power (W) = Energy transferred (J) / time (s)
What equation links
time, power and work done?
P = W/t
Power (W) = Work done (J) / time (s)
Define
conduction.
the process where vibrating particles transfer energy to neighbouring particles
(this occurs mainly in solids because liquids and gases are much more free to move around)
Define
thermal conductivity.
a measure of how quickly energy is transferred through a material by conduction
Define
convection.
the movement of high energy particles from warmer to cooler regions
(this only occurs in liquids and gases because the particles aren’t able to move in solids)
Describe how a
radiator creates convection currents.
(6 steps)
- Energy is transferred from the radiator to the nearby air particles by conduction (the air particles collide with the radiator surface).
- The air by the radiator becomes warmer and less dense.
- This warm air rises and is replaced by cooler air.
- The cooler air is then heated by the radiator.
- At the same time, the previously heated air transfers energy to the surroundings. It thus cools, becomes denser and sinks.
- This cycle repeats, causing a flow of air to circulate around the room - this is a convection current.
What does a
lubricant do?
reduces the friction between objects’ surfaces when they move
(these are usually liquids (like oil), so that they can flow easily between objects and coat them)
What are some things you can do to
prevent energy losses from heating in a house?
(2 things)
- have thick walls that are made from a material with a low thermal conductivity
- use thermal insulation
What are some examples of
thermal insulation?
(4)
- cavity walls
- loft insulation
- double-glazed windows
- draught excluders
What are
cavity walls?
and how do they work as thermal insulation?
an inner and an outer wall with an air gap in the middle
~~~
the air gap reduces the amount of energy transferred by conduction through the walls
cavity wall insulation (where the cavity wall air gap is filled with foam), can also reduce energy transfer by convection in the wall cavity
How does loft insulation work as thermal insulation?
it reduces convection currents being created in lofts
How do double-glazed windows work as thermal insulation?
they work in the same was as cavity walls - they have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows
How do draught excluders work as thermal insulation?
they reduce energy transfers by convection around doors and windows
What is the equation for
efficiency?
useful output (power/energy)x100
~~~~~~~~~~~~~~~~~~~~~~~~~~
input (power/energy)
What device is 100% efficient?
electric heaters
all the energy in the electrostatic energy store is transferred to “useful” thermal energy stores
What are the
three main fossil fuels?
- coal
- oil
- (natural) gas
What are the positives and negatives of
non-renewable energy resources?
(3 points)
+reliable
-will ‘run out’ one day
-do damage to the environment
What are some examples of
renewable energy sources?
(7 examples)
- the sun (solar)
- wind
- water waves
- hydro-electricity
- bio-fuel
- tides
- geothermal
What are the positives and negatives of
renewable energy resources?
(4 points)
+will never run out - the energy can be ‘renewed’ as it is used
+most of them damage the environment, but this is less than non-renewables
-don’t provide much energy
-some are unreliable (because they depend on weather)
How is wind power generated?
- Wind turbines are put up in exposed places.
- Each turbine has a generator inside it.
- The rotating blades turn the generator and produce electricity.
What are the positives of
wind power?
(and wind turbines)(4)
- no pollution (except for manufacture)
- no fuel costs
- minimal running costs
- no permanent damage to the landscape
What are the negatives of
wind power?
(and wind turbines)(5)
- spoil the view
- can be very noisy
- turbines stop when the wind stops or if the wind is too strong
- it’s impossible tp increase supply when there’s extra demand
- the initial costs are quite high
How is solar power generated?
solar panels generate electric currents directly from sunlight
What are the positives of
solar power?
(and solar panels)(4)
- no pollution (except for manufacture)
- very reliable source of energy in sunny countries
- free energy
- very low running costs
What are the negatives of
solar power?
(and solar panels)(3)
- only a source of energy in the daytime
- you can’t increase the power output when there is extra demand
- high initial costs
What are the positives of
geothermal power?
(2)
- reliable
- does very little damage to the environment
What are the negatives of
geothermal power?
(2)
- aren’t very many suitable locations for power plants
- the cost of building a power plant is often high compared to the amount of energy it produces
(only possible in volcanic ares or where hot rocks lie quite near to the surface)
What are the positives of
hydro-electric power?
(5)
- no pollution
- can provide an immediate response to an increased demand for electricity
- no problem with reliability (except in times of drought)
- no fuel costs
- minimal running costs
What are the negatives of
hydro-electric power?
(4)
- there is a big impact on the environment due to the flooding of the valley
- there is possible loss of habitat for some species
- the reservoirs can look very unsightly when they dry up
- initial costs are high
How is wave power generated?
- Lots of small wave-powered turbines are placed around the coast.
- The moving turbines are connected to a generator.
What are the positives of
wave power?
(3)
- no pollution
- no fuel costs
- minimal running costs
What are the negatives of
wave power?
(5)
- disturbs the seabed and the habitats of marine animals
- spoils the views
- can be a hazard to boats
- fairly unreliable, since waves tend to die out when the wind drops
- initial costs are high
How is tidal power generated?
- Tidal barrages (big dams) are built across river estuaries, with turbines in them.
- As tide comes in it fills up the estuary.
- The water is then allowed out through turbines at a controlled speed.
What are the positives of
tidal power?
(5)
- no pollution
- pretty reliable (occur twice a day without fail)
- no fuel costs
- minimal running costs
- has the potential for generating a significant amount of energy
What are the negatives of
tidal power?
(6)
- prevents free access by boats
- spoils the view
- alters the habitat of the wildlife
- height of the tide is variable so energy provided will vary significantly over the year
- moderately high initial costs
- can only be used in some suitable estuaries
What are the positives of
bio-fuels?
(2)
- supposedly carbon neutral
- fairly reliable
What are the negatives of
bio-fuels?
(5)
- cannot respond to immediate energy demands
- the cost to refine bio-fuels is very high
- growing crops specifically for bio-fuels may mean there isn’t enough space or water to meet the demands for crops that are grown for food
- in some regions, large areas of forest have been cleared to make room to grow bio-fuels, resulting in lots of species losing their natural habitats
- the decay and burning of this vegetation also increases carbon dioxide and methane emisssions
What are the positives of
non-renewable energy sources?
(e.g. nuclear energy, fossil fuels)(6)
- reliable
- the power plants can respond quickly to changes in demand
- running costs aren’t that expensive
- fuel extraction costs are fairly low
- nuclear power is clean
- nucelar fuel is relatively cheap
What are the negatives of
non-renewable energy sources?
(e.g. nuclear energy, fossil fuels)(7)
- slowly running out
- high set up costs compared to other energy resources
- coil, oil and gas release carbon dioxide into the atmosphere when they’re burned (adding to the greenhouse effect and global warming)
- burning coal and oil releases sulfur dioxide (which causes acid rain)
- coal mining makes a mess of the landscape
- the view can be spoilt by fossil fuel power plants
- oil spillages cause serious environmental problems, affecting mammals and birds that live in and around the sea
What are the negatives of
nuclear power?
(3)
- nuclear waste is very dangerous and difficult to dispose of
- the overall cost of nuclear power is high due to the cost of the power plant and final decomissioning
- nuclear power always carries the risk of a major catastrophe like the Fukushima disaster in Japan
