why is there three wires in a electric cable?
456654
For the three contacts in a plug which are detailed below.\n\nLive\nThe live contact carries alternating current. The voltage varies by country, as set by national regulations and industry standards. In a few cases (older installations in Scandinavian countries, the outputs of British 110 V building site isolation transformers and probably a few other cases) both main conductors may be live, either being two phases from a three-phase system or being from a single-phase transformer with centre-tapped output. Some plug/socket combinations are designed in a way that a plug can be inserted only one possible way — this is referred to as a polarised plug (not to be confused with positive and negative polarity). Others allow the plug to be inserted with live and neutral either way round — this is referred to as an unpolarised plug. Furthermore even if live and neutral can only mate one way round it may be common to wire them without regard for which is which.\n\n\nNeutral\nThe neutral contact is in most (but not all) cases referenced to the earth. Except under fault conditions it generally does not pose a danger, but is nevertheless treated as live in most installation practices.\n\nThe main danger that can be posed by the neutral is it has a non-null voltage (possibly as high as the voltage on the mains line) after a broken neutral cable in the wiring. Neutral and earth (ground) are strongly related (see Ground (power)) and are usually connected at some point. However extra connections between the Neutral and the Ground must not be made unless the relevant jurisdiction's regulations allow it.\n\n\nEarth\nThe earth contact is only intended to carry current when connected to equipment that has developed an insulation fault (except for EMI/RFI filters which do cause a small current down the earth). If a bare live wire or live component in a device gets loose and touches the metal casing of the appliance, somebody touching the case may receive an electric shock. In many countries devices with metal cases must have the case connected to the ground connection. This reduces but does not eliminate the voltage present on the case relative to earth and metalwork connected to the earthing system.\n\nWhen the neutral is directly connected to the earth as part of the wiring system (a TN system) a fault to earth is a short circuit and therefore provided the wiring is done correctly the circuit breaker will open, or the fuse will blow. In the case of an indirect connection (via the body of the earth) between the earth and the neutral (a TT system) the resistance of the path is much higher and therefore a residual-current device (RCD) must normally be used to disconnect the fault.\n\nThe neutral core could in theory be used as a ground, but this would be dangerous if the core broke, so this is not normally used in building wiring or portable appliances. It is, however, used in some other situations with special precautions. For instance, in Switzerland, sockets in houses with the old two wire installation have the ground and neutral contacts connected together, probably supposing, that the professionally maintained house installation is much more reliable than plugged-in device. Also using the neutral as a ground prevents the use of RCDs.
894062
through transformers and cables
1028768
Simply put, it's not a conductor. \n\nhttp://jchemed.chem.wisc.edu/JCEsoft/CCA/CCA1/MVHTM/R0540/S567.HTM
193841
Chassis ground, This is to prevent shock or fire if there is internal damage. That is why you do not use equipment with the third prong broken off.
391194
I'm assuming you talking about CAT5 or twisted pair cabling. When current runs down a wire a magnetic field is formed introducing noise into the line. By twisting the pairs the magnetic field is interupted and therefore canceling the noise.
568450
Overhead power-lines have a high voltage AC current flowing through them, so create a radiating magnetic field for some distance all around the wires.  When this radiated (moving, because the electricity in the cables is changing direction 60 times a second) passes through the aerial on your radio, it is likely to be at some of the same wavelengths/frequencies as something you are trying to receive deliberatly, so you get "the buzz".\n\nCheck this website out for more:
256669
Because they are not connected to the ground.\n\nElecticity is always trying to move to a ground state, where it experiances least resistance, but it needs a route to get there. As the Birds on the Wire arn't connected to the ground the Electricity has no route to get there and won't travel through the bird/squirrel
347377
At the very basics it has to do with magnetic fields. When a conductor (ie copper wire) is move across (perpendicular to) a magnet-ic field it causes the electrons in the copper wire to move\n\nthis is very basic info and their are other ways like solar cells (due to electron excitment in a different manner)
212526
Trio(s) Elétrico(s).  :)
348214
1.  not enough info\n2.  conduction?\n3.  conductor\n4.  resistance
934121
Ribbon cables are the data lines, there are nine wires in the ribbon cable, 8 carry data--one bit each, either on or off signals to make up the 8 bits for each byte.  Each time a byte of information is transmitted, 8 signals, one for each wire, are sent downt the 8 wires at once.  That's why this is called a parallel system, all eight signals have to go down the wire at the same time running parallel to each other to the receiving end.\n\nThe ninth wire in the ribbon cable is the bit parity signal, either the other 8 signals add up to odd or even according to your system's set up, if the parity bit is even when it should be odd or vice versa, there has been a fault in the data sent down the ribbon cable.  This is the checking system, to make sure there is data integrity in the data being passed between the device and the mother board.\n\nIn essence the ribbon cable is the wire that connects the device (like a hard drive) to the mother board for the purposes of sending data back and forth. While there is current (in micro voltage) running down these lines, they are not the lines that power the device to which they connect or the motherboard, there are power connectors too, these are usually red, yellow and black or blue wires that also connect to the various devices hooked up..they power those devices operation, so you get a power train connected to each device (usually three wires) and a data train (the ribbon cables).
595595
eletricity pasess through a metal wire and then pasess through filiment which not alot of electricity can pas so it is given off as heat and electricity that does make it through goes down another metal wire.
1104792
When the bird perches on a live wire, her body becomes charged--for the moment, it's at the same voltage as the wire. But no current flows into her body. A body is a poor conductor compared to copper wire, so there's no reason for electrons to take a detour through the bird. More importantly, electrons current flow from a region of high voltage to one of low voltage. The drifting current, in effect, ignores the bird. \n\nBut if a bird (or a power line worker) accidentally touches an electrical "ground" while in contact with the high-voltage wire, she completes an electrical circuit. A ground is a region of approximately zero voltage. The earth, and anything touching it that can conduct current, is the ground. \n\nLike water flowing over a dam into a river, current surges through the bird (or person's) body on its way into the ground. Severe injury or death by electrocution is the result. \n\nThat's why a squirrel can run across an electrical line, but sadly die when its foot makes contact with the (grounded) transformer on the pole at wire's end. \n\nIt's also why drivers and passengers are warned to stay inside the car if it runs into a downed power line. Touching the ground with your foot would complete the circuit: Electrons would flow from the wire, into the car, and through you on their way into the earth. (Inside the car you are usually protected by the car's four rubber tires, which act as insulators between car and ground.) \n\nLikewise, birds can get in trouble with power lines if wing or wrist bones--or wet feathers--connect bare wires and grounds. \n\nRaptors (birds of prey) are especially likely to be killed by power lines, particularly in the western U.S. In wide-open plains and deserts, power poles are often the only high perches available for hunters like Bald and Golden eagles and Great Horned owls, who survey the landscape for prey and take off into rising wind currents. \n\nSuch large birds can easily contact two wires or a wire and a transformer with their great wingspread. And raptors can easily brush against a live wire while settling onto a (grounded) pole-top. Thousands are killed by power lines each year. \n\nHow to protect big birds? Power lines can be made less dangerous by widening the gap between conducting and ground wires, insulating wires and metal parts, and moving wires farther away from pole tops. And guards can be built around favorite raptor perches.
875712
Well, actually you can't pull power and low voltage cables in the same conduit and they also cannot share the same outlet box. That would be a violation of NEC (National Electrical Code). This, of course is only a problem for you if you are in the USA and if your authority having jurisdiction (AHJ) has adopted NEC (most in US have but not all). This is a strictly fire related issue (power cables are what usually starts fire and low voltage cables will provide the fuel to make it worse). NEC does not care about EMI (ElectroMagnetic Interference) and it also does not care about performance of your network at all, just its safety to people and property.\nAs far as EMI concerned (if you decided to violate the code and pull them together), CAT5 and higher cables are pretty resilient but metal conduit can exaggerate the detrimental effects of EMI and what hasn't been an issue in an open air environment (you can lay cables close to each other)  will become an issue inside a metal enclosure.\n\nI've provided a resource below for more information about separation of power and data cables
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for a flow in electricity to occur, there has to be a change in voltage.  the bird is touching only one line a very short distance apart.  as there is no difference in voltage between the two points, there can be no traveling of current through the bird.  \n\nalso, the wire offers less resistance to travel than does the bird.  if the roles were reversed, the bird would carry the current.  \n\nand lastly, the wire is insulated.  it's not just bare metal.  this protects the birds and squirrels from the fatal charge.
809231
Ok then, one at a time\n\nwhy are the wires in a plug covered in flexible plastic? - its insulation to stop the individual strands of wire touching each other and causing a short circuit.\n\nwhy is brass used to make the pins in the plug? - 2 reasons, its a very good conductor of electricity and its very strong and resilient to being put in and taken out of the spring loaded metal strips that contact it in a plug.\n\nwhy is the earth pin longer than the others? - its a safety thing, the earth pin goes in first and you cant insert anything into the other two holes until it has - its to stop kids frying themselves if they shove stuff into the holes.\n\nwhy is thick cable used for some appliances and thin for others? - depends upon the amount of current it'll be carrying, a cable for an adaptor for a USB external drive say is thin because it uses a small amount of current, but your electric cooker uses tons, the wire has to be thicker to carry the amount of amperage travelling through it so that it doesn't overheat.\n\nwhat is the purpose of a fuse? - its in case of a power surge, it will blow if too much current passes through it, the fuse blows and not your expensive electrical items.\n\nHope that gave you all you needed to know.
423630
As you must be aware, the voltage on an AC line varies sinusiodally with time. ( it goes from 110v to -110v 60 times a second for a standard wall outlet in the US ). that is why it is called Alternating Current.\nhttp://en.wikipedia.org/wiki/Image:Sine_wave.png\n\nA single AC voltage line and a ground line together are a single phase supply. simple.\n\nNow if you take three cables, with voltages varying over them sinusiodally, you have 3 phase supply :). wish it were that simple though. \n\nnow all three sinusoids will reach their peaks simultaneously, and zeroes simustaneously. the instantaneous power on all the lines would be zero at that point. you can avoid this (and is practically more useful to do so) by staggering these sinusoids, so that they reach 0 at different times. the time by which you stagger them is called the phase difference. the standard is to stagger them by 120 degrees as shown here\nhttp://en.wikipedia.org/wiki/Image:Three_phase_voltages.png\n\nthere you are. hope that is cleared up for you :)