Mechanical energy can also be used to move electrons ...



Current ElectricityWhen electric charge moves we call it current electricity. In most cases the charged particle that moves is the electron, which is negative. Electric current is created by electrons being pushed away by other electrons or electrons being attracted to protons, which are positive.How does this happen?Remember, static electricity can be made by rubbing two different objects together. When this happens, the person doing the rubbing does work. The work moves electrons from one object to another.In this diagram, object A is rubbed with object B. The electrons do not really “want” to go to object B. Since electrons repel each other, they do not like to be put close together on one object. The electrons need to be forced or pushed to object B. Friction causes energy to be released when the objects are rubbed together. This energy is used to push the electrons to object B. 4229100342900002171700800100011430080010002428875113665B00B-1343025-635B00B38709603810B00B17887953810B00B37795207620A00A16306807620A00A485775182880A00A130111567945Energy from friction pushes electronsfrom B to A00Energy from friction pushes electronsfrom B to A2543175144145A00A-1571625148590A00A114300160020Try this: Rub your hands together quickly. Your hands get hot. This is the energy that is used by the electrons.00Try this: Rub your hands together quickly. Your hands get hot. This is the energy that is used by the electrons.Once the electrons get to object B they would like to go back to object A. They cannot because the space between them is too large. However if we connected A and B with a wire the electrons would run down the wire back to A. When the electrons run through the wire it is called current electricity. The problem with our example is that we would have to keep rubbing the objects together to keep moving the electrons to object B and then allow the electrons to run back to A.422910022288500114300188595002057400188595003885565184150B00B1622425165100B00B3729355203835A00A1721485184785A00A55092602667000-16313151343025A00A-1517015314325B00B-1342390125730B00B-163131541910A00AThis is a very slow way to make electricity! There are better ways to “force” electrons to move from one substance to another. Mechanical generators, batteries and solar cells are just a few examples devices that move electrons from one place to another.Small hand crank generators work like this. By turning the handle we make the energy that moves the electrons. When the electrons run back to where they started from they can run through a device like a light bulb and make it glow.Sources of ElectricityBatteriesThere are better ways of moving electrons than rubbing things together. Chemical energy can be used to move electrons. In a battery (or cell) a chemical reaction takes place that releases the energy needed to move electrons from one place to another. In the cell, electrons are taken from the positive terminal and pushed to the negative terminal. If a conductor is connected to the positive and negative terminal the electrons will run from the negative terminal, through the conductor back to the positive terminal. 37719004191000The figure to the right is a cut-away diagram of a typical dry cell. In the middle is a metal rod (in this case a carbon rod). The outside of the cell is made from zinc. Between the two metals is a chemical mixture that moves the electrons from one metal to the other. A finished cell is wrapped with a protective coating.422910010414000A cell acts like a pump. It takes electrons from the positive terminal and “pumps” them to the negative terminal. The electrons run through a conductor back to the positive terminal and start over again. The problem is that in a cell it is a chemical reaction that “pumps” the electrons. Once all of the chemicals have reacted the cell stops “pumping” electrons. When the chemicals are used up the cell is dead. Some cells are rechargeable. They contain chemicals that can be returned to an “unreacted” form when the cell is recharged. DO NOT TRY TO RECHARGE CELLS THAT ARE NOT RECHARGEABLE. Non-rechargeable cells may explode if placed in a battery recharger.Generating Stations Mechanical energy can also be used to move electrons. Generating stations use a variety of ways to turn a “turbine” which in turn causes an electrical generator to convert mechanical moving energy into electrical energy. Electrical energy is produced in generating stations and transported to your home through wires at very high voltages.42291008064500Some types of generation stations:Hydro Generating StationsUse falling water to turn the turbine.46863007112000Fuel Fired Generating Stations (Coal, Natural Gas)Use steam heated by the fuel to turn the turbine.Nuclear Generating StationsUse nuclear reactors to heat the steam that turns the turbine.434340010160000Other Types Of Generating StationsWind – Wind used to turn the turbine.Geothermal – Heat from the earth is used to turn the turbine.Solar-Solar cells are able to change the sun’s energy directly into electrical energy.Electrons and Energy (Voltage)You may have wondered what the difference is between a 9.0 volt cell and a 1.5 volt cell. Inside a cell energy from a chemical reaction is used to push electrons onto the negative terminal. The electrons on the negative terminal are pushing each other away, if given a chance they will run down a wire and through a device to get back to the positive terminal. As the electrons run back to the positive terminal they will lose all the energy they had. In science the unit of volts is used to measure how much energy the electrons in a circuit are carrying. So the electrons in a 9.0 volt cell have more energy than the electrons in a 1.5 volt cell. We often call the energy stored in electrons voltage but the proper name is electric potential. We measure electric potential with a device called a voltmeter.An easy way to visualize electricity is to think of electrons as little carriers of energy. A source (battery, generator etc..) gives energy to the electrons. The electrons carry the energy with them and drop the energy off as they pass through electrical devices. When they return to the source they have given up all their energy so the source gives them more.2057400129540004000500129540003429001295400032004001219200012573001219200022860007620E00E41148007620E00E5715007620E00E4229100000240030000068580000011430010668000CurrentCurrent is used to describe how many electrons are moving through an object like a wire. A high current in a wire means many electrons are moving through the wire and a low current means few electrons are moving through the wire. We measure current with a unit called amperes (or amps for short). As an example, 1 ampere of current would flow through a 100 W light bulb. Since electrons are very small many are needed to make usable current. To get 1 ampere of current 6 250 000 000 000 000 000 electrons must pass through a wire every second! Current is measured with a device called an ammeter. The table below shows the current used by some common electrical devices.Electrical DeviceElectric Current (A)Electronic wrist watch0.0013Calculator0.002Electric clock0.16Fluorescent light bulb0.5100 W light bulb0.83television4.1Electric drill4.5Microwave oven5.0Vacuum cleaner6.5Electric stove element6.8toaster13.6Clothes dryer40Car starter motor500ResistanceNot all substances will allow electrons to move through them freely. Resistance is a measure of how easily electrons can pass through a substance. A substance with a low resistance allows electrons to pass through it easily (a good conductor). A substance with a high resistance is a substance that is very difficult for electrons to move through (an insulator). Conductors are substances that allow electrons to pass through them quite easily. Metals such as gold, copper and aluminum are good conductors.Insulators are substances that do not allow electrons to move through them. Rubber, plastic and wood are good insulators.1143001235075If you were asked to jog down a 100 m long hallway you would use a small amount of energy to get to the other end. If you were asked to jog down a 100 m long hallway with 1.5 m high walls every 5 m that you had to climb over you would work up a sweat getting to the end of the hall. You would lose more energy due to resistance!00If you were asked to jog down a 100 m long hallway you would use a small amount of energy to get to the other end. If you were asked to jog down a 100 m long hallway with 1.5 m high walls every 5 m that you had to climb over you would work up a sweat getting to the end of the hall. You would lose more energy due to resistance!Very few substances have absolutely no resistance. Even good conductors have some resistance. When electrons encounter resistance as they move through a substance they lose energy. The greater the resistance the greater the energy lost. LoadsThe electrical energy the electrons lose from resistance is converted into one of four forms of energy:heat energylight energysound energymechanical energy (energy of motion)5554980762000Loads are devices that have a resistance and remove energy from electrons so that it can be used in different forms. For example the heating element on an electric stove has a high resistance. Electrons lose energy as they pass through it the energy is converted to heat energy.5532120762000Incandescent light bulbs contain a very thin wire made of tungsten. The tungsten wire has a very high resistance. As electrons pass through the tungsten they release energy in the form of heat. The tungsten becomes so hot that it gives off a brilliant white light. Tungsten has a very high melting point so it can be kept very hot without melting or breaking down.29718034290Did you know: Electricity may pass through a 100 km of wire on its way to your house from a generator. Even though the wires are made with good conductors they are so long that the energy loss is noticeable. Some electricity providers charge consumers a percentage of their electrical usage to pay for electric energy lost on the way to your home.00Did you know: Electricity may pass through a 100 km of wire on its way to your house from a generator. Even though the wires are made with good conductors they are so long that the energy loss is noticeable. Some electricity providers charge consumers a percentage of their electrical usage to pay for electric energy lost on the way to your home. ................
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