Transcript The Nature of Energy
The Nature of Energy
What is Energy
• The ability to do work or cause a change is called energy.
• When an organism does work some of its energy is transferred to that object.
Operational Definition
• If a system has energy it has the ability to do something or is actually doing something.
• A system can contain many forms of energy.
Kinetic Energy
• Energy of motion is kinetic energy.
• Two general kinds of energy – kinetic and potential.
Kinetic Energy depends on
• Mass and Velocity • As mass increases so does the kinetic energy.
• As velocity increases so does kinetic energy.
Potential Energy
• Energy that is stored is potential energy. This type of energy has the potential to do work.
• Elastic Potential Energy – is associated with objects that can stretch or compress.
What is work?
• Work is the transfer of energy through motion.
• The amount of work done depends upon two things: • 1. The force exerted • 2. The distance over which force is applied.
Gravity?
• Gravitational potential energy depends on the height of the object.
• PE = weight x height
Background info:
• Gravitational PE on an object is = to the work done to lift it. • Work = Force x Distance • Unit for work and energy is the joule which is = to 1 Newton meter.
Forms of Energy
• Mechanical Energy: • Thermal Energy • Chemical Energy • Electrical Energy • Electromagnetic energy • Nuclear Energy • Sound • Light
Mechanical Energy
• Energy associated with the motion or position of an object.
• Can be Kinetic or Potential.
Thermal Energy
• Total energy of the particles in an object. When thermal energy increases, its particles move faster, making it feel warm to the touch.
Chemical Energy
• Chemical energy is potential energy stored in chemical bonds that hold the chemical compounds together.
Electrical Energy
Moving electrical charges create electricity and the energy they carry is called electrical energy.
Electromagnetic Energy
• It is energy that travels in waves. The waves have some electrical properties and some magnetic properties.
• Light, infrared, microwaves.
Sound Energy
• Energy produced by vibrations causes sound.
Light Energy
• Light energy can cause chemical reactions to occur.
• It provides the energy necessary for photosynthesis in which green plants make their own food through a series of chemical reactions. • It also stimulates chemical reactions in your eyes so that you can see.
Conversions
A change from one form of energy into another.
Law of Conservation of Energy
• This law states that energy can change forms but energy cannot be created or destroyed under ordinary conditions.
A system contains
• Input – the things that go into a system to make it work.
• Output – the things coming out of a system.
• A system must contain input and output.
Balanced
• Many systems require that the input and output of the system are balanced which is not always easy. Consider your own body, what will happen if the input of energy is greater than the output of energy?
Power
• Power is the rate at which work is done in a unit of time.
• Power = work/time • Measured in watts
Energy Sources Discuss cost and benefits of each.
Fossil Fuels
• When plants and animal died, they were covered with layers of sand, mud, ash, and other matter. Great pressure, heat, and bacterial action acted on these buried organisms forming fossil fuels.
Fossil Fuels
• Fuels store energy in the form of Chemical PE. • Fossil fuels include: coal, petroleum, gas.
• The energy fossil fuels store came from the sun.
• Fossil fuels can be burned to release the Potential chemical energy this process is called combustion. PE to thermal E
Examples of Fossil Fuels
• Coal • Petroleum • Natural gas
Non-renewable resources
• All fossil fuels are non-renewable resources – they cannot be replaced after they are used.
• This is why conservation is so important.
Nuclear Energy
• Nuclear Energy is stored in the nucleus of an atom and is released during nuclear reactions. These reactions release a tremendous amount of energy. Nuclear power plants use fission to produce electricity.
Chain Reaction
• 1.
One kind of nuclear reaction occurs when the nucleus splits this is called nuclear fission. In other words when an atomic nucleus splits into two smaller nuclei it is called
nuclear fission
.
• When fission reactions occur in a continuous process it is called a chain reaction.
Nuclear Reactor
• The reactor has to control the chain reaction it uses rods made of boron or cadmium to absorb some of the neutrons. The rods can slow down the chain reaction.
• Eventually energy is released at a constant rate and this is how electricity is produced.
Benefits of Nuclear Energy
• Less harmful to environment in that it produces no air pollution.
Costs of Nuclear Energy
• Hot water from the reactor must cool before it can enter streams and rivers.
• Possibility of radiation escaping from power plants.
• The fission products have long half-lives so they must be stored in containers that will last the period of the radioactive decay.
Nuclear waste:
• Are radioactive by-products that result when radioactive materials are used. They are usually classified from high level to low level wastes for disposal.
• Nuclear waste comes from a variety of sources and is classified according to the level of radioactivity.
Spent Fuel
• 1. Spent nuclear fuel from nuclear reactors.
• Used fuel pellet
• 2.
high level radioactive waste from the reprocessing of spent nuclear fuel.
• 3.
transuranic radioactive waste mainly from nuclear weapons • 4.
• 5.
low level radioactive waste – generally waste from medical and industrial processes.
• 6.
uranium mill tailings from mining and milling of uranium naturally occurring radioactive material.
Low level wastes
• Usually buried in sealed containers in locations licensed by the government.
High level wastes
• Generated by nuclear power plants and by defense research • Stored in heavily insulated cooling pools, and stable containers.
Of Removing Spent Fuel from the Reactors to the Time it’s Ready for Transport!
Spent fuel is a very intensive radiation source that is dangerous for a long time. This high- level waste must not come into contact with the biosphere without first being isolated.
The process of removing spent fuel from the reactors to the time it is ready for transport • Spent fuel stays in the reactor for 3-4 years.
• It is then removed from the reactor. Estimated that about 2000 tons of spent fuel, expressed as the amount of original Uranium in the fuel will be removed from the Finnish reactors during the projected 40 years of operation.
• Spent fuel contained in transportation casks are shipped from nuclear power stations • Casks are temporarily stored in the storage area and then sent to the spent fuel storage building. • Entire process of removing spent fuel from a cask to storage pools are performed underwater.
Spent fuel pool
Step 1: Convectional Nuclear fuel for Reactors Once the fuel has served its time in the reactor it has become spent fuel and is removed from the reactor and stored at the power station for a number of months or years to allow cooling. Following this period it is then ready to be transported.
Step 2: Transports from power stations • Spent fuel are transported from nuclear power stations usually one flask at a time • The fuel is stored on site
It’s all about the process. . .
Nuclear Fusion
• 1.
Another kind of reaction occurs when the nuclei fuse together it is called
nuclear fusion
. • b. HYDROGEN IS THE FUEL FOR THE SUN’S NUCLEAR REACTIONS.
• THE SUN IS POWERED BY NUCLEAR FUSION
Nuclear Fusion
•
The main fuel for the sun’s nuclear reactions is hydrogen. Inside the sun hydrogen nuclei undergo a nuclear fusion reaction that produces helium nuclei. As the two hydrogen nuclei fuse together they release a great deal of energy. This reaction is the major source of energy that the sun now produces.
Alternative Energy Sources
The need for alternatives
Solar Energy
• The sun is the Earth’s only source of new energy.
Hydroelectricity
• Hydroelectricity is the electricity produced by the energy of moving water.
• Dams are built to store water. When the water is allowed to rush out through the tunnels it spins a turbine, rotating the shaft of an electric generator to produce electricity.
Tidal Energy
• The flowing water at low tied spins a turbine, which operates an electric generator.
Wind Energy
• A windmill is a turbine that is turned by wind as it spins it rotates an electric generator • A cost of wind energy is that it looks ugly…
Geothermal Energy
• The inner parts of the Earth contain thermal energy. Wells can be drilled and the steam from within the Earth can be used to rotate turbines.