P1 Flashcards
What is a system?
An object or group of objects
What happens to the system when the energy changes?
The system will then change
Explain what happens and the changes when you throw a ball up to the air
- The initial force exerted by a person to throw a ball upwards does work.
- It causes an energy transfer from the chemical energy store of the person’s arm to the kinetic energy store of the ball and arm.
Explain what happens and the changes when a moving object hits an obstacle
- In a collision between a car and a stationary object, the normal contact force between the car and the object does work.
- It causes energy to be transferred from the car’s 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 might also be transferred away by sound waves.
Explain what happens and the changes when an object is accelerated by a constant force
- A ball dropped from a height is accelerated by gravity.
- The gravitational force does work.
- It causes energy to be transferred from the ball’s gravitational potential energy store to its kinetic energy store.
Explain what happens and the changes when a vehicle slows down
- The friction between a car’s brakes and its wheels does work as it slows down.
- It causes an energy transfer from the wheels’ kinetic energy stores to the thermal energy store of the surroundings.
Explain what happens and the changes when bringing a water to boil in an electric kettle
- The water as the system.
- Energy is transferred to the water (from the kettle’s heating element) by heating, into the water’s thermal energy store (causing the temperature of the water to rise).
Explain what happens and the changes when bringing a water to boil in an electric kettle
- You could think of the kettle’s heating element and the water together as a two-object system.
- 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.
What is the equation for kinetic energy?
Kinetic energy(J) = 0.5 x mass(kg) x speed^2(m/s)
E(k) = 1/2mv^2
What is the equation for elastic potential energy? (Assuming the limit of proportionality has not been exceeded)
Elastic potential energy(J) = 0.5 x spring constant(N/m) x extension^2(m)
E(e) = 1/2ke^2
(Equation is in the physics equation sheet)
What is the equation for gravitational potential energy?
Gravitational potential energy(J) = mass(kg) x gravitational field strength(N/kg) x height(m)
E(p) = mgh
How do you find the change in thermal energy?
Change in thermal energy(J) = mass(kg) x specific heat capacity(J/kg C) x temperature change(C)
△E = mc△θ
Practical / Just in case for later
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What is power?
The rate at which energy is transferred or the rate at which work is done
State the two equations to calculate power
Power(W) = Energy transferred(J) / Time(s)
P = E/t
Power(W) = Work done (J) / Time(s)
P = W/t
What is an energy transfer of 1 Joule equal to?
1 Watt
Give an example that illustrates the definition of power
- Take two cars that are identical in every way apart from the power of their engines
- Both cars race the same distance along a straight race track to a finish line.
- The car with the more powerful engine will reach the finish line faster than the other car- i.e. it will transfer the same amount of energy but over less time.
What is the conservation of energy principle?
Energy can be transferred usefully, stored or dissipated,but can never be created or destroyed.
What is a ‘closed system’?
- 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 zero.
Give an example of an energy transfer for closed systems
- A cold spoon is dropped into an insulated flask of hot soup, which is then sealed.
- You can assume that the flask is a perfect thermal insulator so the spoon and the soup form a closed system.
- Energy is transferred from the thermal energy store of the soup to the useless thermal energy store of the spoon (causing the soup to cool down slightly).
- Energy transfers have occurred within the system, but no energy has left the system - so the net change in energy is zero,
Why is dissipated energy called ‘wasted energy?’
As the energy is being stored in a way that is not useful (usually energy has been transferred into thermal energy stores).
Give an example of how the system changes when there is dissipated energy
- A mobile phone is a system.
- When you use the phone, energy is usefully transferred 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 (you may have noticed your phone feels warm if you’ve been using it for a while).
What can lubricants do to frictional forces?
- For objects that are being rubbed together, lubricants can be used to reduce the friction between the objects’ surfaces when they move.
- Lubricants are usually liquids (like oil), so they can flow easily between objects and coat them.
The higher the thermal conductivity of a material the higher….?
The rate of energy transfer by conduction across the material
How can you prevent energy loss through heating in your homes?
- Have 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 the building will cool more slowly).
- Use thermal insulation
What are the two equations to calculate efficiency?
Efficiency = useful output energy transfer / total input energy transfer
Efficiency = useful power output / total power input
How can you improve the efficiency of an intended energy transfer?
- Insulating objects
- Lubricating them
- Making them more streamlined
What are the main energy resources on Earth?
- Fossil fuels (coal,oil and gas)
- Nuclear fuel
- Bio-fuel
- Wind
- Hydro-electricity
- Geothermal
- The tides
- The sun
- Water waves
What is a renewable energy resource?
An energy source that is being or can be replenished as it is used
What are the uses of energy resources?
- Transport
- Electricity
- Generation and heating
Give examples of energy resources that are non-renewable
- Coal
- Oil
- Natural gas
Give examples of energy resources that are renewable
- Sun
- Wind
- Water
- Waves
- Hydro-electricity
- Bio-fuel
- Tides
- Geothermal
Definition of non-renewable energy resources
- Non-renewable energy resources are fossil fuels and nuclear fuel (uranium and plutonium).
- Fossil fuels are natural resources that form underground over millions of years.
- They are typically burnt to provide energy.
- They are finite
Characteristics of renewable energy resources
- These will never run out - the energy can be ‘renewed’ as it is used.
- Most of them do damage the environment, but in less nasty ways than non-renewables.
- The trouble is they don’t provide much energy and some of them are unreliable because they depend on the weather.
State how non-renewable are used in transport
Petrol and diesel powered vehicles (including most cars) use fuel created from oil.
Coal is used in some old-fashioned steam trains to boil water to broduce steam
State how renewable are used in transport
Vehicles that run on pure bio-fuels or a mix of a bio-fuel and petrol or diesel (only the bio-fuel bit is renewable, though).
State how non-renewable are used in electricity generation
Unknown
State how renewable are used in electricity generation
Unknown
State how non-renewable energy resources are used in heating
- Natural gas is the most widely used fuel for heating homes in the UK. The gas is used to heat water which is then bumbed into radiators throushout the home.
- Coal is commonly burnt in fireplaces.
- Electric heaters (sometimes called storage heaters) which use electricity generated from non-renewable energy resources
State how renewable energy resources are used in heating
- A geothermal (or ground source) 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.
- Burnine bio-fuel or using electricity generated from renewable resources can also be used for heating.
Why are some energy resources more reliable than others?
- Some energy resources are more reliable than others.
- The non-renewable sources are the most reliable as they can be used at any time.
- Whereas, the renewable sources normally depend on the weather.
- This means that if there is no wind, or no sun (night-time), or no waves then no electricity can be generated.
What is the environmental impact arising from the use of different energy resources
- The environmental problems directly related to energy production and consumption include air pollution, climate change, water pollution, thermal pollution, and solid waste disposal.
- The emission of air pollutants from fossil fuel combustion is the major cause of urban air pollution.
However, with renewable energy sources becoming more popular and becoming more eco-friendly, the only problems that account to it is the fact that it is limited by money,reliability and politics
Explain the patterns and trends in the use of energy resources
1) Over the 20th century, the electricity use of the UK hugely increased as the population grew and people began to use electricity for more and more things.
2) Since the beginning of the 21st century, electricity use in the UK has been decreasing (slowly), as we get better at making appliances more efficient (p.172) and become more careful with energy use in our homes.
3) Some of our electricity is produced using fossil fuels and from nuclear power.
4) Generating electricity isn’t the only reason we burn fossil fuels - oil (diesel and petrol) is used to fuel cars, and gas is used to heat homes and cook food.
5) However, we are trying to increase our use of renewable energy resources.
This move towards renewable energy resources has been triggered by many things…
Issues from the use of different energy resources
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