Electricity usually means the movement of electrons. (It can also be the movement of protons). And, electric force is much much larger - I mean really greater - than gravity.
The electric charge is named for the property of the electron that gives its force! and the charge of proton is q=1.6X10^-19 [Col] and the charge of electron is -q.
Electric current is a flow of electric charges - charged particle movement.
1[A] = 1 [Col]/1[sec] --> I = Q/t [A]=[Col/sec]
How many electrons much flow for 1 A of current?
--> 1 [Col] = 1/q = 6.25X10^18 [electrons], thus for 1A = 6.25 X 10^18 electrons must flow per second.
Metal: electrons can flow easily through it
Glass: lights can easily pass through it
Electrons can move easily inside a piece of metal, but they can't easily leave the surface of the metal. They are held back by the attraction of the positively-charged nuclei. Free movement of electrons can take place only if the moving electrons are replaced by other electrons. For this reason, electron current usually flows in circle or closed paths.
(ex1) electric code have two wires in it.
(ex2) Coaxial cable - TV tube serves as the electron "return path"
(ex3) When a bird lands on an electric power line, some electrons will immediately flow into the bird. But with nowehere to go, the electrons soon repel other electrons from coming, so the flow will stop. Very few electrons are needed to stop the flow.
Resistance
ex1) tunsten (high resistance) is used in filament in a light bulb so that it first generate heat then later light. Exept illuminating part (made of tungsten) in the bulb, the rest of electricity must flow through low resistance wire, such as copper.
ex2) fuse has high resistance so that when much current flows through it, it blow out. Other wires in a house are made of coppers.
Volt and electron energy
Amps tell you how many electrons are flowing past a point each second.
Volts tell you the energy of the electrons.
The energy unit called the electron volt or eV is defined as "1eV = 1.6 X 10^-19 [J]".
The eV is a typical amount of energy for a single atom or molecule!!!!!!
(Note)
If a piece of metal has a largee number of electrons, each with energy of 1eV, the metal is at one volt!!
--> a voltage of one volt or a potential of one volt
It is okay to refer to the energy of an electron in volts, rather than in eV.
Remember that when a piece of metal is at one volt, it means that every electron in that metal has that energy!!!!
To know the power, you must know the energy per particle AND the number of particles per second. In static electricity, for those daily sparks we feel, the voltage was probably between 40,000 and 100,000V! Yet it doesn't kill us because the current is low, limited by the small number of electrons we picked up. However, a similiar voltage in the back of TV set is very dangerous. That's because the amount of current that can flow to you is much greater.
Electric Power
The power delivered by electrons depends on the energy of the electrons, and the number per second that arrive!
1-volt electron is 1.6 X 10^-19 [J]
1-amp means 6 X 10^18 electrons per second flow.
Thus, 1[V] X 1[A] = 1 [J/sec] = [W]. ==> Power = Volt X Amp
Note that high votlage does not always mean high power. If the amps are tiny, then high voltage can be safe! It is important for you to know tha thigh voltage is not dangerous if there isn't much currnet and if it doesn't last for very long.
- Lighting: high voltage and high current --> dangerous!
House Power
The power company works very hard to keep the voltage at 120V even when you start using more appliances. The voltage doesn't change, only the current!!
In US, V = 120, Power (in W) = 120 X current (in amps).
Thus, a appliance has current of Power/120.
In Europe, the typical house voltage is 240V rather than 120V. This means that for typical power, the voltage is higher and the current is less. Higher voltage makes the electricity more dangerous than in the US, but lower ucrrent means that there is less energy lost in the wires that deliver electricity to the outlet. (or, alternatively, it means that they can use cheaper wires without getting too much heating)
Most long-distance transmission of electricity is done at extremely high voltage, several tens of thousands of volts. High-voltage lines have less current (for the same power delivered) than do low-voltage lines. But heating from resistance depends only on the current, not on the voltage! So, if we use high-voltage lines, then we can reduce the amps, and that reduces the loss of power from resistive heating!!!!
Since high voltage can make electricity dangerous, there are special devicess that raise the voltage V and lower the current I, while keeping the power P unchanged. - transformer!
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