Combined Physics - 6.1 Flashcards
In physics, what is a ‘system’?
A system is an object or group of objects
What changes are involved in the way energy is stored in an object projected upwards?
Chemical Energy → Kinetic Energy → Gravitational Potential Energy
What changes are involved in the way energy is stored in a moving objecting hitting an obstacle?
Kinetic Energy → Sound Energy / Thermal Energy
What changes are involved in the way energy is stored in an object accelerated by a constant force such as gravity when dropping a ball?
Gravitational Potential Energy → Kinetic Energy
What changes are involved in the way energy is stored in a vehicle slowing down?
Kinetic Energy → Heat Energy
What changes are involved in the way energy is stored bringing water to a boil in an electric kettle?
Electrical Energy → Thermal Energy
What equation is used to calculate the kinetic energy of a moving object?
How can the gravitational potential energy gained by a raised object above the ground be calculated?
What is the specific heat capacity of a substance?
The amount of energy required to raise the temperature of 1kg of the substance by 1oC
What is power?
The rate at which energy is transferred / the rate at which work is done
What are the three equations associated with power?
What energy transfer is equal to a power of 1 watt?
1 joule per second
Lifting an object takes 10’000J – machine A can do this in 50s but machine B takes 100s. Which machine is more powerful?
Both machines transfer the same amount of energy, but machine A is more powerful:
P = W ÷ t
Machine A has a power of 200W (10’000 ÷ 50) whilst machine B has a power of 100W (10’000 ÷ 100)
What is the conservation of energy principle?
Energy can be transferred usefully, stored or dissipated but never created or destroyed
What happens to the energy transfer in a closed system?
There is no net change to the total energy
When energy is transferred not all of it is transferred usefully (some energy is dissipated). What term is used to describe this dissipated energy?
Wasted energy
How does lubrication reduce unwanted energy transfers?
Lubrication reduces frictional forces
How does insulation reduce unwanted energy transfers?
Insulation reduces the rate of energy transfer by heating
List some examples of insulation
- Cavity wall insulation (reduces convection)
- Loft insulation (reduces convection)
- Double-glazed windows (reduces conduction)
- Draught excluders (reduces convection)
What is conduction?
Conduction is the process where vibrating particles transfer energy to neighbouring particles (occurring mainly in solids)
What is convection?
Convection is the process where energetic particles move away from hotter regions to cooler ones (occurring in fluids)
In terms of conduction across the material what does an increased thermal conductivity of a material cause?
Increased thermal conductivity of a material means a higher rate of energy transfer
How do walls and the thermal conductivity of the material affect the rate of cooling in a building?
Thick walls made from a material with low thermal conductivity slows the rate of energy transfer (so the building remains warmer for longer)
What is the equation for energy efficiency for a given energy transfer, with regard to energy input/output?
What is the equation for energy efficiency for a given energy transfer, with regard to power input/output?
Higher Q. How can the efficiency of an intended energy transfer be increased?
Insulation, lubrication of more streamlined (reducing frictional forces)
What are the main energy resources available on Earth?
- Fossil fuels
- Nuclear fuel
- Bio-fuel
- Wind
- Hydro-electricity
- Geothermal
- Tidal
- Solar
- Water waves
List the types of fossil fuel
- Coal
- Oil
- Gas
What does the term non-renewable energy resource mean (and list them)?
Non-renewable energy resources will run out, e.g. coal, oil, natural gas and nuclear
What does the term renewable energy resource mean (and list them)?
Renewable energy resources can be replenished (will never run out), e.g. solar, wind, water waves, hydro-electricity, bio-fuel, tidal and geothermal
What uses do we have for energy resources?
- Transport
- Electricity generation
- Heating
Describe wind power and how it is used
Wind turbines are placed in exposed areas where rotating blades turn a generator producing electricity. They are non-polluting (though spoil the view / are noisy)
Describe solar cells and how they are used
Solar cells generate electricity directly from sunshine. They are non-polluting (though don’t work at night)
Describe geothermal power and how it is used
Geothermal power relies on naturally occurring hot rocks which heat pumped water creating steam. They cause very little damage to the environment (though there are few locations available)
Describe hydro-electric power and how it is used
Hydro-electric power uses falling water (usually falling over a dam). Though this is clean energy, the construction of the dam can be extremely damaging (high levels of concrete / habitat damage etc…)
Describe water wave power and how it is used
Water wave power uses wave-powered turbines around the coast generating electricity.
Describe tidal barrages and how they are used
Tidal barrages are dams built across river estuaries, using the Sun and Moon’s gravity where the tide turns a turbine. Non-polluting they do change the habitat
Describe bio-fuels and how they are used
Bio-fuels are made from plants and waste which are supposedly carbon neutral. Costs are high and bio-fuel crops reduce space for food crops
What energy resources are used for transport?
Petrol / diesel from oil is mainly used (though coal for steam engines / bio-fuels are also used)
What energy resources are used for heating?
Natural gas is mainly used for heating, though coal and electric heaters are also used. Solar water heaters are also becoming more common
Why are non-renewable energy resources so abundantly used?
Non-renewables are relatively cheap and are reliable (there is enough to meet current demand)
What environmental issues do non-renewable energy resources create?
Fossil fuels release CO2 into the atmosphere contributing to global warming. Acid rain is also caused, along with nuclear power potential disasters / oil spillages etc…
What current trends in energy resource use exist at present?
The world currently heavily depends on fossil fuels, though people are increasing wanting to use more renewables (e.g. electric cars)
Why is renewable energy uptake limited?
Currently renewable energy isn’t as reliable or cost effective as non-renewable energy. Politics of increased initial prices for renewable energy resources also often gets in the way
