P1 Flashcards
What is a system?
A system is an object or a group of objects
What is a closed system?
A system where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero
What are the 8 energy stores?
- kinetic energy store
- gravitational potential energy store
- elastic potential energy store
- chemical energy store
- thermal(internal) energy store
- nuclear energy store
- electrostatic energy store
- magnetic energy store
What are the four ways energy can be transferred?
- mechanically
- by heat
- by radiation
- electrically
State the conservation of energy
Energy cannot be created or destroyed. It can only be transferred usefully, stored or dissipated
Explain what happens as water boils in an electric kettle
energy is transferred to the water by heating, into the water’s thermal energy store and this causes the temperature of the water to rise
What is work done?
the amount of energy transferred
Explain what happens when an object (e.g. a ball) is projected upwards
- the initial force exerted by a person to throw a ball does work.
- Energy is transferred from the chemical store of the arm to the kinetic energy store of the ball and arm and the gravitational potential energy store of the ball
Explain what happens as a car slows down
- the frictional forces cause a transfer of energy
- energy is transferred from the wheels’ kinetic energy store to the thermal energy store of the surroundings
What is the equation to calculate kinetic energy?
kinetic energy = 0.5 × mass × (speed)^2
Ek= joules
mass= kg
speed= m/s
What is an elastic potential store?
any object that is stretched, twisted or compressed
How can you calculate the elastic potential energy in a stretched spring?
elastic potential energy = 0.5 × spring constant × (extension)^2
Ee= joules
Spring constant(k)= N/m
extenstion= m
equation for gravitational potential energy
Gravitational potential energy= mass x gravity x (change in) height
Ep= joules
mass=kg
gravity= N/Kg e.g. Earth=9.8
height= metres
equation to calculate the amount of energy stored in/ released from a system as its temperature changes?
Change in thermal energy= mass x specific heat capacity x temperature change
Δ E = m c Δ θ
mass= kg,
shc(c)= J/kg°C
What is internal energy?
The energy stored inside a system by particles that make up the system. Internal energy is the total kinetic energy and potential energy of all particles in the system
What is specific heat capacity?
The amount of energy it takes to raise the temperature of 1kg of a substance by 1 degree Celsius.
What effect does thermal conductivity have on the rate of energy transfer?
The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material
Explain how a convection current works
A convection current is formed by a constant transfer of energy by heating to the substance. As the air is heated it becomes less dense so it rises whilst the cold air sinks. Once the heated air is away from the heater it becomes colder and then sinks allowing the hot air to rise. This then continues in a cycle
Why are runners given foil blankets?
The heat would reflect light (infrared radiation) off the surface and back to heat the runners
How can you make your walls in your home reduce the amount of energy wasted?
- having thicker walls
- having walls made with a material with a LOW thermal conductivity (less energy transfer via conduction)
What else may be put in place in homes to reduce energy transfer?
- loft insulation
- double glazed windows
- cavity wall insulation
- fit carpets
What are the roles of lubricants?
Lubricants reduce the friction between the surfaces of objects that are rubbing together
Define power
power is the rate at which energy is transferred or the rate at which work is done
What is the equation linking power, energy transferred(or work done) & time?
P= E/t, power=energy transferred/time
P=W/t
power=work done/ time
True or False: An energy transfer of 1 joule per second is equal to a power of 1 watt
True
Define efficiency
Efficiency is the proportion of input energy transferred which is usefully transferred
What are the two equations for efficiency?
- efficiency=useful output energy transfer/ total input energy transfer
- efficiency= useful power output/ total power input
How can the efficiency of a system be increased?
- reducing waste output-by lubrication, thermal insulation
- recycling waste output- recycling thermal waste energy as input energy
How can the efficiency of a mechanical machine with moving parts be improved?
Lubricate any moving parts to reduce the friction and therefore energy loss due to heating
How can the efficiency of a radiator be improved?
Installing metal foil sheets behind the radiator to reflect the heat back into the room rather than it being absorbed into the walls
What is a non-renewable energy resource?
A non-renewable energy resource is one that has a limited supply & it will run out at some stage because they are used faster than they can be replaced
What are the main energy resources available for use on Earth?
- fossil fuels(coal, oil, gas)
- biofuels(plant products, animal dung)
- nuclear fuel(uranium, plutonium)
- wind
- solar
- geothermal
- hydro-electricty
- tides
- waves
What is a renewable energy source? give examples
A renewable energy resource is one that can be replenished as it is used
- solar
- wind
- biofuels
- geothermal
- hydro-electricity
- waves
- tidal barrages
Give examples of non-renewable energy resources
- fossil fuels
- nuclear power
Give 2 advantages and 2 disadvantages of fossil fuels
Advantages
- fossil fuels are easy to obtain
- fossil fuels provide a cost effective energy resource
Disadvantages
- The carbon dioxide produced adds to the greenhouse effect
- burning coal releases sulfur dioxide which causes acid rain
Give 2 advantages and 2 disadvantages of nuclear power
Advantages
- less fuel offers more energy
- no carbon dioxide is produced
Disadvantages
- the waste is hard to dispose of
- gives off harmful waste products
Give 2 advantages and 2 disadvantages of biofuels
Advantages
- fairly reliable as plants take a short time to grow
- biodiesel has a higher flash point, which means it is safer as it does not ignite easily
- carbon neutral: it uses the same amount as any carbon it produces so there’s no overall release of carbon
Disadvantages
- high costs are needed to refine biofuels
- large amounts of water and space are needed to grow the crops
Give 2 advantages and 2 disadvantages of wind power
Advantages
- produces no pollution
- no fuel costs
- does not cause any permanent damage to the landscape
Disadvantages
- no power when the wind stops
- can be very noisy
- can not increase the supply when there is a higher demand as it relies on the wind
-visual pollution
Give 2 advantages and 2 disadvantages of solar cells
Advantages
- produces no pollution
- energy is free and the running costs are almost nil
- perfect for providing energy for devices that do not need large amounts of energy
Disadvantages
- no energy at night when there is no sun (can only be generating during daytime)
- generates energy on a relatively small scale
Give 2 advantages and 2 disadvantages of geothermal power
Advantages
- free energy
- reliable
- very little impact on the environment
Disadvantages
- there are not many suitable location for the power stations
- building costs for the power stations are very high
Give 2 advantages and 2 disadvantages of hydro-electric power
Advantages
- no pollution
- can provide an instant response to an increased demand of energy
Disadvantages
- environmental impacts e.g. rotting vegetables
- reservoirs look unpleasant when they dry up
Give 2 advantages and 2 disadvantages of wave power
Advantages
- no pollution
- no fuel costs
- can be useful on small island
Disadvantages
- can be a hazard to boats
- disturbs the seabed and the habitats of marine animals
Give 2 advantages and 2 disadvantages of tidal barrages
Advantages
- no pollution
- no fuel costs
- has the potential for generating large amount of energy
Disadvantages
- spoils the view and alters the habitat
- the height of the tide is a variable
- prevents free access by boats
