energy Flashcards
What happens when energy is transferred?
When energy is transferred, the energy is stored in one of the object’s energy stores.
Name eight types of energy.
types of energy:
- thermal
- chemical
- kinetic
- magnetic
- gravitational potential
- electrostatic
- elastic potential
- nuclear
Name four ways in which energy can be transferred.
Energy can be transferred mechanically, electrically, heating or radiation.
What happens when energy is transferred by heating?
When energy is transferred by heating, heat transfers to the object’s thermal energy store.
What two things can happen when energy is transferred by doing work?
When energy is transferred by doing work, a force either moves an object, or a voltage moves a charge, causing a current.
What happens when energy is transferred by falling objects?
When an object falls, they are accelerated by gravity, so gravitational potential energy is lost. This lost energy is almost equal to the energy gained by the kinetic energy store, but air resistance causes some GPE to be lost to other stores.
How do you calculate kinetic energy?
kinetic energy (J) = 0.5 x mass (kg) x speed^2 (m/s)
How do you calculate work done?
work done (J) = force (N) x distance (m)
What happens when energy is transferred by lifting an object?
Lifting an object in a gravitational field causes an increase in gravitational potential energy.
What is the gravitational field strength on Earth?
gravitational field strength on Earth - 9.8 N/kg
How do you calculate gravitational potential energy?
gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
When is energy transferred to the elastic potential energy store?
When a force is applied to change the length of an object (stretched or squashed), energy is transferred to the elastic potential energy store.
What is specific heat capacity?
Specific heat capacity is the energy required to raise the temperature of 1 kg of a substance by 1°C.
What is the specific heat capacity of water?
The specific heat capacity of water is 4200 J/kg°C
What is the conservation of energy?
conservation of energy
- energy can be transferred usefully, stored or dissipated (‘wasted’)
- however, energy can never be created or destroyed
What is power?
Power is the rate at which energy is transferred or work is done.
How do you calculate power?
power (W) = energy transferred OR work done (J) / time (s)
What is 1W?
1W is 1J of energy transferred every second.
Why are some machines more powerful?
Machines are usually more powerful if they transfer more energy in a shorter amount of time.
What is conduction?
Conduction is the process of vibrating particles transferring energy to neighbouring particles in solids.
How does conduction work?
conduction
- heat causes particles to gain more kinetic energy
- in a solid, the particles are closer together
- this causes energy to be transferred at faster rate
- once the object is heated, the surroundings are
What is the thermal conductivity of an object?
The thermal conductivity is a measure of how easily an object conducts thermal energy.
- the higher the thermal conductivity of an object, the higher the rate of energy transfer across the material
Why are metals better conductors than other objects?
Metals are better conductors as they have delocalised electrons which are free to move through the metal, and they move in between particles to transfer the kinetic energy faster.
What is an insulator?
An insulator is not efficient at conducting heat.
How do insulators work?
The particles in insulators are not directly next to each other, so energy cannot be transferred easily.
What is convection?
Convection is the heat transfer in liquids and gases.
Describe the process of convection when there is a constant source of heat.
convection
- heat transfer in liquids and gases
- when you heat a region of a liquid or gas, the particles move faster
- this means that the space between particles get smaller, causing the density to decrease
- this heated region rises due to the loss in density and the denser, cooler region sinks to take its place
- if there is a constant heat source, a convention current is made
Why can the process of convection not occur in solids?
Convection currents cannot occur in solids as the particles are in fixed positions, so they can’t rise or fall to create a convection current. If the state is changed, then they can do this.
What is a system?
A system is an object or a group of objects.
What is a closed system?
A closed system is an object or group of objects where no energy can enter or leave, so there is never a change in the total energy.
How can energy be transferred in unwanted ways?
In a system, energy is transferred in unwanted ways, such as thermal energy through friction with air particles.
Name two ways of reducing unwanted energy transfers.
reducing unwanted energy transfers
- lubrication
- insulation
Describe how lubrication reduces unwanted energy transfers.
lubrication
- reduces friction and air resistance by removing air particles and creating a barrier for them
Name a lubricant.
lubricant - oil
Describe how insulation reduces unwanted energy transfers.
insulation
- reduces the rate of energy transfer by heating
- thick walls are made from a material with a lower thermal conductivity, so less thermal energy is lost
Give three examples of insulation in real life situations.
examples of insulation
- cavity walls have an air gap or foam between two walls to reduce conduction
- loft insulation is usually with fibreglass wool to prevent conduction and convection
- double-glazed windows have an air gap to reduce conduction
How do you calculate efficiency?
efficiency = useful output of energy transfer (J) or power (W) / total input of energy transfer (J) or power (W)
How can the efficiency of an object be increased?
Increase the efficiency of an object by wasting less energy or power - ensure that as much input energy or power as possible is transferred to the useful output.
Name one object that is 100% efficient and state why.
100% efficient
- electric heaters as all the energy in the electrostatic energy store is transferred to useful thermal stores
Why is (almost) nothing 100% efficient?
Nearly everything is not 100% efficient as wasted energy is usually transferred to thermal stores due to friction mainly.
Why are LED bulbs more efficient than incandescent bulbs?
LED bulbs are more efficient than incandescent bulbs as they transfer a higher percentage of the input energy to light energy rather than thermal.
What is renewable energy?
Renewable energy is an energy resource that can be replenished as it is used.
What is non-renewable energy?
Non-renewable energy is an energy resource that cannot be replenished.
Give three uses of energy.
uses of energy
- transport
- generating electricity
- heating
Name two non-renewable sources of energy.
non-renewable energy
- fossil fuels
- nuclear
Name seven renewable sources of energy.
renewable energy
- wind
- solar
- hydro-electric
- tidal
- wave
- geothermal
- bio-fuels
What percentage of the world’s energy is fossil fuels?
Coal, oil and gas supply about 80% of the world’s energy. This proportion is decreasing.
Give five advantages of fossil fuels.
advantages of fossil fuels
- reliable
- they release a great deal of energy
- abundant
- cheap
- versatile (a range of uses; transport, generating electricity, heating…)
Give three disadvantages of fossil fuels.
disadvantages of fossil fuels
- releases lots of CO2
- non-renewable, so will run out
- releases other pollutants, like sulfur dioxide
What is wind energy?
Wind energy is when the wind turns blades, which turn a generator to produce electricity. However, they cannot be used in fueling transport.
Give three advantages of wind energy.
advantages of wind energy
- never run out
- once it is built, there are no CO2 emissions
- cheap to sustain
Give four disadvantages of wind energy.
disadvantages of wind energy
- not pleasing to the eye
- unreliable
- noisy
- initial costs are high
What is solar energy?
Solar energy is when sunlight is converted to electricity through solar panels. However, they cannot be used in fueling transport.
Give three advantages of solar energy.
advantages of solar energy
- never run out
- once it is built, there are no CO2 emissions
- cheap to sustain
Give three disadvantages of solar energy.
disadvantages of solar energy
- unreliable
- initial costs are high
- not many suitable locations
What is hydro-electric energy?
Hydro-electric energy is when falling water through rocks turns turbines, which turns a generator to produce electricity. However, they cannot be used in fueling transport.
Give four advantages of hydro-electric energy.
advantages of hydro-electric energy
- never run out
- once it is built, there are no CO2 emissions
- very reliable
- cheap to sustain
Give three disadvantages of hydro-electric energy.
disadvantages of hydro-electric energy
- initial costs are high
- habitats are destroyed through floods
- only useful in countries with lots of rivers
What is tidal energy?
Tidal energy is when the tide flows, which turns turbines to turn a generator, which generates electricity. However, they cannot be used in fueling transport.
Give four advantages of tidal energy.
advantages of tidal energy
- never run out
- once it is built, there are no CO2 emissions
- cheap to sustain
- extremely reliable, as the tide is inevitable
Give two disadvantages of tidal energy.
disadvantages of tidal energy
- initial costs are high
- harms wildlife
What is wave energy?
Wave energy is when waves force air into turbines, which turn them, which turn generators which generate electricity. However, they cannot be used in fueling transport.
Give five advantages of wave energy.
advantages of wave energy
- never run out
- once it is built, there are no CO2 emissions
- reliable
- huge potential in the UK
- cheap to sustain
Give two disadvantages of wave energy.
disadvantages of wave energy
- experimental
- initial costs are high
What is geothermal energy?
Geothermal energy is when cold water is pumped into the earth, and steam from the heat of the earth is used to power turbines, which turn generators which generate electricity. However, they cannot be used in fueling transport.
Give four advantages of geothermal energy.
advantages of geothermal energy
- never run out
- once it is built, there are no CO2 emissions
- reliable
- very few environmental problems
Give one disadvantage of geothermal energy.
disadvantage of geothermal energy
- rarely used as there are very few suitable locations
What are bio-fuels?
Bio-fuels are made from plant materials and animal waste. It can be solid, liquid or gas. It is burnt to produce electricity or run cars.
Give three advantages of bio-fuels.
advantages of bio-fuels
- never run out
- carbon neutral, burning produces CO2 but this is taken in by other plants
- fairly reliable
Give two disadvantages of bio-fuels.
disadvantages of bio-fuels
- if the land is used to grow crops for fuel, which could push up the price of food
- still experimental
What is nuclear power?
Nuclear power runs on uranium and plutonium.
Give three advantages of nuclear power.
advantages of nuclear power
- once running, they release no CO2
- reliable
- produce lots of energy
Give three disadvantages of nuclear power.
disadvantages of nuclear power
- non-renewable
- they contain very dangerous radioactive materials, and if there is an accident, they will be released
- radioactive waste needs to be stored for thousands of years before they are safe
- at the end of they power plant’s life, it needs to be decommissioned, which takes years and is expensive
Give three reasons why we are trying to increase the use of renewable energy.
why we are increasing renewable energy
- pressure from the public
- release less emissions than non-renewable
- don’t run out
Give six problems with renewable energy.
problems with renewable energy
- increases taxes
- building new renewable energy power plants costs money, so we stick with current ones
- some require specific locations
- most aren’t as reliable
- more research is needed which takes time and money
- electric cars are expensive
