P2 Flashcards
Define work done
Work done is energy transferred
What is the equation for work done? What is its unit of measurement?
W=F x d
Work done= force applied to the object x straight line distance it moves
Produces product of Nm (newton-meters)
Work is measured in joules (J)
1J=1Nm
How does force relate to energy gained/lost?
If a force acts in the direction an object is moving -> gain energy (usually kinetic energy)
If force acts in the opposite direction an object is moving -> lose energy (usually heat energy)
Give one example of work
Ball
Ball is lifted to a height above the ground
Energy is transferred from kinetic energy store to gravitational potential energy store
Weight on the ball (via gravity) does the work on the ball
Bird
Travel against air resistance
Chemical energy store to kinetic energy store to thermal energy store (dissipated as heat )
What is a system?
An object or a group of objects
What is the principle of energy conservation?
Energy cannot be created or destroyed, only transferred from one store to another
List all (ones on guide) types of energy stores (8)
Kinetic
Gravitational
Elastic
Electrostatic
Magnetic
Chemical
Nuclear
Thermal
Kinetic - energy an object had because its moving (a result of its mass and speed)
Gravitational - energy an object has due to its position above the ground (mass and height above the surface)
Elastic - energy stored in a stretched material
Electrostatic - energy due to a force of atttraction/repulsion between two charges
Magnetic- energy due to forces of attraction/repulsion between 2 magnets
Chemical - energy found in fuel, food, batteries/ Transferred during chemical reactions
Nuclear - energy contain in the nucleus of an atom
Thermal - energy a substance has due to temperature
Name all (ones on guide) energy transfer pathways
Mechanical
Electrical
Heating
Radiation
Mechanical - force acts on a body
Electrical - transfer energy from a power source (ex: cell delivering to components)
Heating - thermal energy transferred by conduction, convection, radiation
Radiation - light and sound carry energy, transfer between two points
What is an example of kinetic energy?
A vehicle moving
What is an example of chemical energy?
Potential energy in the bonds of chemical compounds
When a bond break chemical energy -> heat energy (exothermic)
When bond created heat energy -> chemical energy (endothermic)
What is an example of gravitational potential energy?
Energy stored in an object due to its position in a gravitational field (book sitting on a shelf)
What is an example of elastic potential energy?
Energy stored in an elastic body due to deformation (compress a spring -> energy used to compressed -> stored in spring)
What is an example of nuclear energy?
Energy released from nuclear fission (splitting of large nucleus) /fusion
How is heat energy measured? Why?
More heat -> more energy = increased vibration of atoms and molecules
Measured using the average kinetic energy of particles
Temp not equal to heat energy
What does electrical energy create?
Energy required for charged particles to move through a conductor (current created)
What is light energy?
Light-> created from heat and kinetic and chemical
Created due to a disturbance in electric and magnetic fields
What is sound energy?
Movement of energy through vibrations of matter in longitudinal waves
What is the equation for kinetic energy?
KE = ½ × mass × velocity^2
What is the equation for the gravitational potential energy?
ΔEP = mgΔh
ΔEP = change in gravitational potential energy, in Joules (J)
m = mass, in kilograms (kg)
g = gravitational field strength in Newtons per kilogram (N/kg)
Δh = change in height in metres (m)
What is wasted energy?
When energy is dissipated into the surroundings by radiation in a ‘closed system’, the energy lost is called wasted energy
This is because the energy is usually not useful
What is efficiency?
A measure of how well energy is transferred in a system
The ratio of useful power/energy transfer output to its total power/energy transfer input
What is the typical efficiency of a thermal power station?
30% - meaning 70% of energy produced is wasted energy
How is power related to work done and time taken? What is the equation relating to this?
Power is the rate at which work is done,
Power is the work done per unit time.
P=W /t or change in energy/t
E or W = The energy transferred, or work done, measured in joules (J)
t = time measured in seconds (s)
P = power measured in watts (W)
What is the difference between renewable and non renewable sources of energy?
Renewable -> cannot deplete over time (ex; sunlight, water,wind, geothermal)
Non renewable - will deplete over time (fossil fuels)
What are examples of fossil fuels?
Coal
Natural gas (methane)
Boliers and cookers
Crude oil (petroleum, diesel, etc)
What are fossil fuels made of?
Fossil fuels are formed from the remains of plants and animals
Sunlight -> chemical energy/chemical store
What are some advantages of fossil fuel?
Readily available
Reliable for large scale energy production (not so much as time goes on)
What are some disadvantages of fossil fuel?
Takes million+ years for fossil fuel to form
Non renewable energy source
Increased demand -> increased prices
Predicted to run out within 200 years
Pollution (CO2, SO2, etc)
What are some uses of fossil fuel?
Transport:
Most vehicles -> fuel from crude oil
Electric vehicles -> powered by national grid -> uses both renewable and non renewable sources
Electricity:
Energy when needed (on demand)
Coal burned -> water boil -> steam -> turbine -> generator
84% of energy -> non renewable sources (Environmental impact)
Heat:
Colder countries -> central heating
Natural gases to heat water (radiators)
What is bio fuel?
Fuel made from plant matter
Can be used in place of fossil fuels
Half of energy density of fossil fuels
What are advantages of bio fuel?
Renewable resource
Biofuel -> carbon neutral
No SO2 either
What are disadvantages of bio fuel?
Crops must be grown -> takes time
Takes from food
Still releases carbon -> but carbon neutral because absorbed by plants
How are waves and tides used to generate energy?
Waves: turn turbines
Tides:high tide on one side of the barrage -> flow to other side -> turn turbine
What are advantages of water as an energy source?
No pollution
Reliable -> large amount on short notice
Renewable
What are disadvantages of using water as an energy source?
Expensive to build
Damages habitats
Suitable for few location
Technology is not advanced enough for large scale production
How do hydroelectric dams work?
Water is stored above ground level -> has gravitational potential store
Energy transfer to kinetic energy when if flows down a slope -> turn turbine
What are advantages of hydroelectric dams?
Respond to demand -> reliable and available
Generate at a large scale
What are disadvantages of hydroelectric dams?
Need to flood valleys -> destroyed habitats and towns
Pumping system -> release large amounts of greenhouse gas
How are geothermal energy sources used?
Radioactive material underground release energy as it decays -> geothermal energy -> heats rocks to a high temperature
Water poured vis shafts underground -> heated by rocks -> retuned to surface as hot water or steam -> turn turbine
What are the advantages of geothermal energy sources?
Renewable resource
Reliable
Smaller-> less land used
What are the disadvantages of a geothermal energy source?
Few suitable locations (only small scale)
Release greenhouse gas underground
Expensive
How is nuclear fission used to ‘produce’ energy?
Energy stored in nucleus -> released if nucleus is broken into two (nuclear fission)
Used in nuclear power stations
What are some advantages of nuclear fission?
No pollution
Safe (as long as they are working properly -> safety checks and precautions)
Generate on a reliable and large scale
What are some disadvantages of nuclear fission?
Uranium ore (used in fission) is limited
Produces radioactive waste
Accident occurs at nuclear reactor -> waste can leak and spread
How is heat + light from the sun transferred?
Energy from sun -> transferred via radiation
Solar energy -> Low energy density (many devices needed)
What are solar cells?
They transfer energy from sunlight -> produces a current and generates electrical power
Can be stored in batteries
What are advantage of solar cells?
Renewable
Sunlight is a reliable source (depends on location)
No greenhouse gas or pollution
Generated in remote places
What are disadvantages of solar cells?
Large scale/area to produce large amounts
Expensive
Visual pollution
Sunlight may not be a reliable energy source
What are solar panels?
Transfer energy from sunlight to a thermal store -> used to heat water
Used to warm domestic water supplies
Reduce cost of heating water
Solar furnaces -> mirrors used to focus sun onto a small area -> used to boil water -> steam -> turbine
What are the advantages of solar panels?
Renewable energy source
Sunlight is reliable (some locations)
No greenhouse gases or pollution
Cut cost of energy for households
What are the disadvantages of solar panels?
Solar furnaces -> large scale to be useful -> expensive
Energy is still needed to heat water in households
Sunlights may not be a reliable source
How is wind energy used to ‘generate’ electric energy?
Wind turns the turbine -> rotation of blades turns a generator -> electricity
What are the advantages of wind energy?
No greenhouse gas
Renewable
What are the disadvantages of wind energy?
Noise/visual polllution
Accidents with birds
Need wind present
Expensive
Why is the sun so important for energy sources (excluding geothermal, nuclear, tidal)? (Wind water biofuel)
Sun heats atmosphere -> air expands and starts to move -> convection current -> creates wind
Extension: -> wind moves the sea (friction) -> waves
Water evaporates and falls because of sun -> fills up reservoirs (water)
Plants growth required sunlight -> biofuels and fossil fuels
EXCEPTIONS:
Geothermal -> heat from core
Nuclear -> elements that make up earths crust
Tidal -> mainly moons gravitational force
How is energy released by nuclear fusion (the suns core)? Why would it be useful for humans?
Nuclear fusion -> collision + bonding of hydrogen nuclei to form helium nuclei, and releasing nuclear energy
Could be used to generate energy on earth -> basically solves all problems (limitless carbon-free generation)
BUT:
High temps required (like sun level)
-> scientist researching how to make temps lower
Right now -> requires the same amount of energy as it produces
What is the equation for efficiency?
Efficiency = useful energy output/total input x 100%
(Or energy can be replaced by power (E or W/t)
