Physics - Topic 1 - Energy

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  • Created by: hannah.o
  • Created on: 02-02-18 20:07
What happens when energy is transferred?
When energy is transferred to an object, the energy is stored in one of the object's energy stores.
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What are the 8 energy stores?
Thermal, Kinetic, Gravitational potential, Elastic potential, Chemical, Magnetic, Electrostatic, and Nuclear.
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How is energy transferred?
Mechanically (by a force doing work), electrically (work done by moving charges), by heating or by radiation (e.g light or sound).
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What is a system?
A single object (e.g. the air in a piston) or a group of objects (e.g. two colliding vehicles).
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What happens when a system changes?
When a system changes, energy is transferred. It can be transferred into or away from the system, between different objects or between different types of energy stores.
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What are closed systems?
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.
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How is energy transferred to a kinetic energy store?
Energy is transferred to this store when an object speeds up and is transferred away from this store when an object slows down.
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What is the equation for kinetic energy?
Ek = 1/2 x mass x speed^2
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What is the equation for gravitational potential energy?
g.p.e = mass x gravitational field strength x height
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What happens when something falls?
When something falls, energy from its gravitational potential energy store is transferred to its kinetic energy store.
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What is the equation for a falling object when there's no air resistance?
energy lost from the g.p.e store = energy gained in the kinetic energy store
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What is the equation for elastic potential energy?
Ee = 1/2 x Spring constant x extension^2
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When can you not use this elastic potential energy equation?
When the limit of proportionality has been exceeded.
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What is specific heat capacity?
Specific heat capacity is the amount of energy needed to raise the temperature of 1 kg of a substance by 1'C.
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What is the equation for specific heat capacity?
Change in thermal energy = mass x shc x temperature change
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In the SHC practical, why insulate the block of substance?
To reduc the energy transferred from the block to the surroundings.
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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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What is power?
Power is the rate of energy transfer, or the rate of doing work.
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What is power measured in?
Watts (W)
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What is the equation for power?
Power = Energy transferred or Work done / Time
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What is conduction?
Conduction is the process where vibrating particles transfer energy to neighbouring particles.
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What is thermal conductivity?
It is a measure of how quickly energy is transferred through a material.
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What is convection?
Convection is where energetic particles move away from hotter to cooler regions.
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How can a convection current be created?
If there is a constant heat source.
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Which air rises?
Warm air
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What is a convection current?
A flow of air which circulates - warm air rises and is replaced by cooler air which is then heated. The previously heated air transfers energy to the surroundings. This repeats.
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What can you used to reduce frictional force?
Lubricants.
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How do lubricants reduce frictional force?
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, so they can flow easily between objects and coat them.
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What reduces the rate of energy transfer by heating?
Insulation
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What can you do to prevent energy losses though heating?
Have thick walls that are made from material with a low thermal conductivity. The thicker the walls and the lower their thermal conductivitym the slower the rate of energy transfer will be so the building will cool more slowly.Use thermal insulation
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What are 4 examples of thermal insulation?
Cavity wall, loft insulation, double-glazed windows, and draught excluders.
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How do cavity walls work?
Made up of an inner and outer wall with an air gap between, which reduces the amount of energy transferred by conduction. Cavity wall insulation, where the cavity wall air gap is filled with a foam, can also reduce energy transfer by conduction
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How does loft insulation work?
Loft insulation can reduce convection currents being created in lofts.
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How do double-glazed windows work?
They work in the same way as cavty walls - they have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows.
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How do draught excluders work?
Draught excluders around doors and windows reduce energy transfers by convection.
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How is a device more efficient?
When less energy is wasted.
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How can you improve the efficiency of energy?
Insulating objects, lubricating them or making them more streamlined.
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What is the 1st equation for efficiency?
Useful output energy transfer/ total input energy transfer
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What is the 2nd equation for efficiency?
Useful power output/ Total power input
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What are non-renewable energy resources?
Fossil fuels and nuclear fuel.
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What are fossil fuels?
Fossil fuels are natural resources that form underground over millions of years. They 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 will all non-renewable resources do?
They will all run out. They all do damage to the environment but they provide most of our energy.
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What are the 7 renewable energy resources?
The Sun (solar), wind, water waves, hydro-electricity, bio-fuel, tides, geothermal
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What will all renewable resources do?
They will never run out. Most of them do damage the environment, but in less nasty ways than non-renewables, They don't provide much energy and some are unreliable as they depend on the weather.
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What can energy resource be used for?
Transport and heating
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What does wind power involve?
Putting lots of wind turbines up in exposed places.
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What does each turbine have?
Each turbine has a generator inside it - the rotating blades turn the generator and produce electricity.
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What are the advantages of wind power?
No pollution. There are no fuel costs and minimal running costs.
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What are the disadvantages of wind power?
Spoil the view, very noisy, initial costs are high and the turbines may stop working when the wind stops, and it is impossible to increase supply when there's extra demand.
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How do solar cells generate electricity?
Solar cells generate electric currents directly from sunlight.
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Where is solar power used?
Solar power is often used in remote places where there's not much choice and to power electric road signs and satellites.
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What are the advantages of solar power?
No pollution. It is a very reliable source of energy, especially in sunny countries. The energy is free and running costs almost 0.
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What are the disadvantages of solar power?
Can't increase the power output when there is extra demand. Initial costs are high and are used to generate electricity on a small scale.
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Where is geothermal power possible?
In volcanic areas or where hot rocks lie quite near to the surface. The source of much of the energy is the slow decay of various radioactive elements, including uranium, deep inside the Earth.
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What are the advantages of geothermal power?
Free energy, reliable, does very little damage to the environment. It can be used to generate electricity, or to heat buildings directly.
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What are the disadvantages of geothermal power?
There aren't many suitable locations for power plants, and the cost of building a power plan is often high compared to the amount of energy it produces.
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What does hydro-electric power require?
The flooding of a valley by building a big dam. Water is allowed out through turbines.
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What are the advantages of hydro-electric power?
No pollution, can provide an immediate response to an increased demand for electricity, no fuel costs and minimal running costs, it can be a usefu way to generate electricity on a small scale in remote areas, and is fairly reliable.
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What are the disadvantages of hydro-electric power?
Big impact on the environment due to the flooding of the valley (rotting vegetation releases methane and CO2) and possible loss of habitat for some species. The reservoirs can also look very unsightly when they dry up.
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What is needed to produce wave power?
Lots of small wave-powered turbines located around the coast. These are connected to generators.
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What are the advantages of wave power?
No pollution, no fuel costs and minimal running costs. Can be very useful on small islands.
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What are the disadvantages of wave power?
Disturbing the seabed and the habitat of marine animals, spoiling the view and being a hazard to the boats. They are fairly unreliable and wave power is never likely to provide energy on a large scale.
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How are tides most commonly used?
Building a tidal barrage.
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What are tidal barrages?
Tidal barrages are big dams built across river estuaries, with turbines in them. As the tide comes in it fills up the estuary. The water is then allowed out through turbines at a controlled speed.
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How are tides produced?
Tides are produced by the gravitational pull of the Sun and the Moon.
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What are the advantages of tidal barrages?
No pollution, pretty reliable, no fuel costs and minimal running costs. Has the potential for generating a significant amount of energy.
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What are the disadvantages of tidal barrages?
They prevent free access by boats, spoil the view and alter the habitat of the wildlife. The height of the tide is variable so lower tides will provide less energy. They don't work when the water level is the same either side of the barrage.
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What are bio-fuels?
Bio-fuels are renewable energy resources created from either plant products or animal dung. They can be solid, liquid or gas and can be burnt to produe electricity or run cars in the same way as fossil fuels.
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What are the advantages of bio-fuels?
Supposedly carbon neutral, fairly reliable.
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What are the disadvantages of bio-fuels?
They cannot respond to immediate energy demands. The cost to refine bio-fuels is very high. Some worry that growing crops specifically for bio-fuels will mean there isn't enough space or water to meet the demands for crops for food.
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Large areas of forest may have to be cleared to make room to grow bio-fuels, resulting in the loss of habitats. The decay and burning of vegetation increases CO2 and methane emissions.
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What fuels/energy are reliable?
Fossil fuels and nuclear energy.
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Why are fossil fuels and nuclear energy reliable?
There's ennough to meet current demand, and they are extracted from the Earth at a fast enough rate that power plants have fuel in stock.
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What are the advantages of fossil fuels and nuclear energy?
Can respond quickly to change in demand. Running costs aren't that expensive and fuel extraction costs are fairly low so using fossil fuels is a cost effective way to produce energy.
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What are the disadvantages of fossil fuels and nuclear energy?
The fuels are slowly running out and set up costs are high. Coal, oil and gas release CO2, which adds to the greenhouse effect and global warming. Burning coal and oil releases sulfur dioxide which causes acid rain. Views can be spoilt.
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Oil spillages cause serious damage to the environment, affecting mammals and birds that live in and around the sea. Nuclear waste is very dangerous and difficult to dispose of.
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Other cards in this set

Card 2

Front

What are the 8 energy stores?

Back

Thermal, Kinetic, Gravitational potential, Elastic potential, Chemical, Magnetic, Electrostatic, and Nuclear.

Card 3

Front

How is energy transferred?

Back

Preview of the front of card 3

Card 4

Front

What is a system?

Back

Preview of the front of card 4

Card 5

Front

What happens when a system changes?

Back

Preview of the front of card 5
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