Unit 1 - Energy Flashcards
Unit of measure for power
Watts (W)
Power (W) =
Power (W) = energy transferred (J) / time (S)
Formula to calculate average power
P = Fv
Power (W) = force (N) X velocity (m/s)
Definition for work
“work” is when you are moving a subject over a certain distance, with a certain force. This movement is called work
Work is measured in
Joules (J)
Work done (J) =
Work done (J) = Force (N) X distance (M)
What are the main components of a power station (fossil fuel)
Generator, turbines, boiler, condenser, fuel
Problems with fossil fuel power stations
Cause global warming and air pollution
Gravitational potential energy (GPE) is measured in
Joules (J)
GPE (J) =
Gravitational potential energy (J) = mass (kg) X gravity (g / usually 10 on Earth) X height (m)
Kinetic energy (J) =
KE (J) = 0.5 X mass (kg) X velocity²
GPE on earth is usually
10 N/Kg
Define energy
Energy is the capacity to do work. Measured in Joules (J)
What happens when force is applied perpendicular to the direction of movement ?
No work is done (not useful)
Elastic potential energy =
Energy stored (J) = average force (N) X distance (m)
Unit of measure for energy
Joule (J), kilojoule (KJ)
Breaking distance (m)
Breaking distance (m) = Kinetic energy (J) / force (N)
( When thrown vertically )
Height (m) =
Height (m) = KE / (mass X gravity)
State the law for conservation of energy
Energy cannot be created or destroyed, only transferred
Work done (J) =
Work done (J) = force (N) X distance (M)
Time (s) =
Time (s) = energy (j) / power (w)
Energy transferred (j) =
Energy (j) = power (w) X time (s)
Efficiency (%) =
Efficiency (%) = (useful energy output / total energy input) X 100
Name the types of energy
Chemical, thermal, kinetic, gravitational potential (GPE), elastic potential, sound, light
Speed (or velocity) =
Speed (m/s) = distance (m) / time (s)
What is conduction
Conduction is direct transfer by contact.
Why is conduction best in metals
Metals are the best conductors of energy because they have free electrons
How does conduction take place
Atoms vibrate and pass that vibrations on to the atom nearest to them by colliding and ‘shaking’ them. Because of this, conduction a works best where atoms are closer together (best in solids, worst in gases)
What is convection
Convection is the circulation of a fluid (liquid or gas) caused by heating it
How does convection occur
Heating a fluid makes it less dense so the hot fluid rises. Once the fluid rises, it cools and falls back towards the heat source causing a convection currant. This circulation continued until the fluid is in equilibrium
What is infrared radiation
Infrared radiation is energy transfer by electromagnetic waves
What objects emit infrared radiation
All object that are above absolute zero (-273C or 0K) emit infrared radiation.
Hotter objects emit more infrared radiation
How does infrared travel
As electromagnetic waves.
Because of this, infrared can travel through a vacuum as it does not need particles to be transferred.
What objects reflect the most infrared radiation
Light coloured, shiny, smooth objects reflect the most infrared radiation
What objects absorb the most infrared radiation
Dark coloured, rough, matt surfaces absorb the most infrared
What role does convection take in everyday phenomena
Coastal wind is caused by convection currants.
Air above land warms up quicker than the air above the sea. The air above land rises and moves towards the sea, cools and is pushed back towards land causing an inward wind. This cycle in reversed at night.
How is insulation used in buildings
Insulation is used to stop heat transfers.
Examples of insulation is double glazed windows (air in between glass reduces conduction) and cavity wall insulation (foam in between walls containing small pockets of gas to reduce conduction and convection)
How is insulation used to reduce energy transfers from the human body.
Layers of fat under the skin insulate the human body.
Clothes are also used to stop conduction away from the body.
Describe the energy transfers involved in harnessing wind energy
Kinetic energy (wind) –> mechanical + kinetic energy (turbines) –> electrical energy + heat
Describe the energy transfers involved in generating water power (aka hydropower)
GPE (height of water) –> kinetic energy (water dropping)
–>mechanical / kinetic energy (turbines) –> electrical energy + heat
Describe the energy transfers involved in harvesting geothermal energy
Thermal energy (heat from geothermal resource) –> thermal energy (water) –> kinetic energy (steam) –> mechanical / kinetic energy (turbines) –> electrical energy + heat
Describe the energy transfers involved in solar cells
Infrared radiation (sun) –> electrical energy + heat
Describe the energy transfers involved in solar heating systems
Thermal energy (sun) –> thermal energy (heating water)
Describe the energy transfers involved in harvesting energy through fossil fuels
Chemical energy (fuel) –> thermal energy (burning fuel) –> thermal energy (heating water) –> kinetic energy (steam) –> mechanical / kinetic energy (turbines) –> electric energy + heat
[ the smoke and pollution are produced in the 2nd step when the fossil fuels are burnt and smoke is produced ]
Describe the energy transfers involved in harvesting nuclear power
Thermal energy (nuclear reactor) –> thermal energy (heating water) –> kinetic energy (steam) –> mechanical / kinetic energy (turbines) –> electrical energy + heat
Describe the pros and cons of wind energy
Pro: wind is free, renewable energy source
Con : unreliable, eyesore, high maintenance, low efficiency
Describe the pros and cons of water energy
Pro : can re-use water, no greenhouse gases produce
Con : dam failure will cause mass destruction, very noisy
Describe the pros and cons of geothermal energy
Pro: renewable energy, no pollution, very efficient
Con: can only be harvested in certain areas, can’t be moved easily
Describe the pros and cons of solar heating systems
Pro: lowers water bill, renewable energy
Con: not efficient, expensive to purchase and install
Describe the pros and cons of solar cells
Pro: renewable, can be used anywhere sunny
Con: not efficient, expensive
Describe the pros and cons of fossil fuels
Pro : produce lots of energy cheaply, very efficient
Con: produces lots of greenhouse gases
Describe the pros and cons of nuclear power
Pros : produce LOADS of energy, energy sources not likely to run out of thousands of years
Cons: produce nuclear waste, can be used to make nuclear weapons
Velocity (speed) =
Speed (m/s) = distance (m) / time (s)
