# physics topic 1

what are the energy stores?
thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear
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how can energy be transferred?
mechanically, electrically, by heating, by radiation
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what is a system?
a single object, or group of objects, that you're interested in
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what happens when a system changes?
energy is transferred, either into or away from the system, between different objects in the system or between different types of energy stores
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what are closed systems?
systems where neither matter nor energy can enter or leave, so the net change in energy is always zero
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what energy transfers occur in a kettle?
energy is transferred electrically to the thermal energy store of the kettle's heating element, which transfers energy by heating to the water's thermal energy store
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how is work done?
when current flows (work done against resistance in a circuit), or by a force moving an object
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what energy transfers occur when a person throws a ball?
the initial force exerted by the person does work, causing an energy transfer from the chemical energy store of the person's arm to the kinetic energy store of the ball and arm
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what energy transfers occur when a car brakes?
the friction between a car's breaks and its wheels does work as the car slows down, causing an energy transfer from the wheel's kinetic energy stores to the thermal energy store of the surroundings
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what energy transfers occur when a car collides with a stationary object?
the normal contact force between the car and the object does work, causing energy to be transferred from the car's kinetic energy store to other energy stores like the elastic potential and thermal energy stores of the object and car, or sound waves
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what energy transfers occur when a ball is dropped?
the gravitational force does work, and as it falls, energy from its gpe store is transferred to its kinetic energy store
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what effect does air pressure have on falling objects?
it acts against falling objects, causing some energy to be transferred to other energy stores (eg. thermal energy stores of the object and surroundings)
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what causes energy to be transferred to a kinetic energy store?
energy is transferred to this store when an object speeds up, and is transferred away when an object slows down
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what causes energy to be transferred to a gpe store?
lifting an object in a gravitational field reuqires work, causing a transfer of energy to the gpe store, and the higher it's raised the more energy will be transferred
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what causes energy to be transferred to a epe store?
stretching or sqaushing an object transfers energy to this store
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what is meant by specific heat capacity?
the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree
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what is the conservation of energy principle?
energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
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describe the energy transfers for a mobile phone (open system)
energy is transferred usefully from the chemical energy store of the battery in the phone, but some of this energy is dissipated in this transfer to the thermal energy store of the phone
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describe the energy transfers for a cold spoon in hot soup (closed system)
energy is transferred from the energy store of the soup to the useless thermal energy store of the spoon (net energy change is zero as no energy has left the system)
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what is power?
the rate of energy transfer
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what is a powerful machine?
a machine which transfers lots of energy in a short space of time
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what is conduction?
the process where vibrating particles transfer energy to neighbouring particles
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what is thermal conductivity?
a measure of how quickly energy is transferred through a material via conduction
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what is convection?
where energetic particles move away from hotter to cooler regions
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how does friction cause energy to be dissipated?
whenever something moves, there will be at least one frictional force, which causes some energy in the system to be dissipated (eg. air resistance)
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how do lubricants reduce friction?
lubricants are usually liquids, so they can easily flow between objects and coat them, making it easier for them to slide over one another
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how do thick walls reduce energy transfers in a house?
the thicker the walls and the lower their thermal conductivity, the slower the rate of energy transfer will be, so the slower a house will cool down
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how do cavity walls reduce energy transfers in a house?
they have an air gap between the inner and outer walls, reducing the amount of energy transferred through the walls, and cavity wall foam can reduce transfers by convection
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how does loft insulation reduce energy transfers in a house?
fibreglass wool is often used, which is a good insulator as ir has pockets of trapped air, reducing energy loss by conduction and preventing the creation of convection currents
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how do double-glazed windows reduce energy transfers in a house?
they have an air gap between 2 sheets of glass, preventing energy transfer by conduction through the windows
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how do draught excluders reduce energy transfers in a house?
placing them around doors and windows reduces energy transfers by convection
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what makes a device efficient?
the less energy that is dissipated in the useless energy store, the more efficient it's said to be
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how do you improve efficiency?
insulating, lubricating, making the object more streamlined
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what is the only device that is 100% efficient?
electric heaters, as all of the energy is transferred to useful stores
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what is a fossil fuel?
natural resources that form underground over millions of years and are typically burnt to provide energy
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what are the 3 main fossil fuels?
coal, oil, natural gas
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what are the features of fossil fuels?
will run out one day, do damage to the environment, provide most of our energy
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what are 3 renewable energy resources?
the sun, wind, tides
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what are the features of renewable energy resources?
will never run out (can be renewed), do damage to the environment but not as seriously as fossil fuels do, don't provide much energy and are unreliable
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which non-renewable resources are used in transport?
petrol and diesel powered cars use fuel from oil, coal is used in some steam trains to boil water and produce steam
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which renewable resources are used in transport?
some vehicles run on pure bio-fuels or a mix of a bio-fuel and petrol/diesel
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which non-renewable resources are used in heating?
natural gas is used to heat water which is then pumped into radiators, coal is often burnt in fireplaces, some electric heaters use electricity from non-renewable resources
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which renewable resources are used in heating?
geothermal heat pumps use geothermal energy resources to heat water, solar water heaters work by using the sun to heat water which is pumped into radiators, burning bio-fuels or electricity can be used to generate heat
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how do wind turbines work?
each turbine has a generator in it, with blades that turn the generator and produce electricity
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what are the advantages of wind turbines?
no pollution, no fuel costs and minimal running costs, no permanent damage to the landscape
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what are the disadvantages of wind turbines?
spoil the view, very noisy, stop when the wind stops or is too strong, can't increase supply with extra demand, initial costs are high
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how do solar cells work?
solar cells generate electric currents directly from sunlight
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what are the advantages of solar cells?
no pollution, very reliable in sunny countries but can also be cost-effective in cloudy countries, energy is free and running costs are almost zero, can be used in remote places where there isn't much choice of energy sources
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what are the disadvantages of solar cells?
can't increase power output with extra demand, initial costs are high, can usually only generate energy on a small scale
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how does geothermal power work?
energy from underground thermal energy stores is used
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what are the advantages of geothermal power?
brilliant free energy, reliable, few environmental problems
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what are the disadvantges of geothermal power?
only possible in volcanic areas where hit rocks lie near the surface so not many suitable locations, cost of building the power plant is high compared to the amount of energy produced
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how does hydro-electric power work?
requires the flooding of a valley and the building of a big dam which catches rain water and then lets it out through turbines
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what are the advantages of hydroelectric power?
can provide an immediate response to increased demand, reliable except from in times of drought, no fuel costs and minimal running costs
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what are the disadvantages of hydroelectric power?
big impact on the environment due to the flooding of the valley which causes vegetation to rot and produce methane, causes loss of animal habitats, reservoirs look unattractive when dried up
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how does wave power work?
there are lots of wave powered turbines located around the coast connected to a generator
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what are the advantages of wave power?
no pollution, no fuel costs and minimal running costs
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what are the disadvantages of wave power?
disturbs the seabed and marine animals' habitats, spoils the view, is a hazard to boats
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how do tidal barrages work?
tidal barrages are big dams built across river estuaries with turbines in them, and as the tide comes in it sfills up the estuary, and is them allowed out through the turbines at a controlled spees
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what are the advantages of tidal barrages?
no pollution, reliable in that tides happen twice a day every day, no fuel costs and minimal running costs
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what are the disadvantages of tidal barrages?
prevents free access by boats, spoils the view, alters the habitat of wildlife
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how do bio-fuels work?
biofuels are created from plant products or animal dung, and can be burnt to produce electricity or to fuel cars
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what are the advantages of bio-fuels?
supposedly carbon neutral (has been debated as plants must be grown at the same rate as they are burnt for this to work), fairly reliable as crops don't take very long to grow and different crops can be grown all year round
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what are the disadvantages of bio-fuels?
cost of refining them is very high, growing them may mean that there isn't enough space or water to grow crops for food, clearing areas to grow them in destroys habitats and produces co2
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evaluate the use of fossil fuels
they're reliable, there are enough to meet current demand, can be extracted quickly to respond to changes in demand, they're slowly running out however and will run out if no new resources are found, low extraction costs makes them cost effective
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what causes acid rain?
burning coal and oil releases sulfur dioxide, which causes acid rain, which can be harmful for trees and soils
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how can acid rain be reduced?
taking the sulfur out before the fuel is burned, or by cleaning up the emissions
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what do oil spillages cause?
can cause serious environmental problems affecting mammals and birds that live in and around the sea
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evaluate the use of nuclear fuel
nuclear power is clean but nuclear waste is very dangerous and difficult to dispose of, nuclear fuel is relatively cheap but the overall cost of nuclear power is high due to the cost of the power plant and final decommissioning, risks a catastrophe
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what has been the trend for fossil fuel usage in the 20th/21st century?
in the 20th century electricity usage increased as the population grew, since the 21st century electricity use has decreased as appliances become more efficient and we become more careful with how we use electricity
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how has better knowledge of fossil fuels led to them being used less?
we now know that burning fossil fuels is very damaging for the environment, making people want to use more renewable resources that damage the environment less
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how have people and governments led to fossil fuels being used less?
people and governments are increasingly aware that non-renewables will run out one day, and so people think it's better to learn how to get by without them before this happens
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how has pressure from other countries led to fossil fuels being used less?
governments have begun to introduce targets for using renewable resources, which puts pressure on energy providers to build new power plants that use renewable resources so that they don't lose business and money
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how have car companies led to fossil fuels being used less?
electric cars and hybrids are on the market and their popularity is increasing
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what limits the use of renewables?
scientists can't make people change their behavior, buidling new power plants costs money and there are arguments over where they would be built, some renewables aren't as reliable as fossil fuels, research on improving renewables takes time/money
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why is making personal changes to reduce fossil fuel use expensive?
hybrid cars are more expensive than equivalent petrol cars, solar panels are still quite expensive
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## Other cards in this set

### Card 2

#### Front

how can energy be transferred?

#### Back

mechanically, electrically, by heating, by radiation

### Card 3

#### Front

what is a system?

### Card 4

#### Front

what happens when a system changes?

### Card 5

#### Front

what are closed systems?

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