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(bas)French this page, General electricity, understanding
- batteries ; DC, AC. Static electricity
Cells and batteries
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Lighting
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Electrical current understanding
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Electric power
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Measures
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Electric dangers
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Nature of the electrical current
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Static electricity.
CELLS AND BATTERIES
The technological development as regards refillable
batteries encourages to me to open a new page because they are part of our
daily life, with the lamps, the machines and the fuses or circuit breakers
which burn see
brico.
The price of the cells
we are at the era of the cells and if you do not know how much they cost to you, try to summarize them one day. For two retired
persons like us, without toys and with a minimum of pile apparatuses, this is yet 150/ 200 € a year.
With children, a little loved too much of course, it could become five or six times more !
You must to know that the cells and batteries are a juicy market
and that manufacturers, who cut down prices for apparatuses themselves or
sell them with a loss, get benefits with the sale of the cells in an
indirect way. There too, there must be "back margins".
That is to say they probably make apparatuses consuming more than they could.
Obscure information; cells do not read any information on
their capacity, i.e. the quantity of energy they contain. Why then batteries
mention them ? manufacturers say that it is too variable to be mentioned;
it is a little true but not too much, because you can see, by noting the
dates, that your radio set die more or less the same time. They prefer
by far to indicate "new", "super power", "special radio", "extra long
duration" etc instead of giving a mere figure. Make yourself the tests of
ratio price quality. I tested cells of the own store
brand, hardly less expensive, which did not last anything.
Cells can really be unequal; one or two cells of a play can
be exaggeratedly weak whereas the others are still correct;
before discarding, check them all with a cells tester or more
simply with a bulb of flashlight (1, 35 volts for example), with an electric
cord. You can thus replace only the weakest cells.
The cells which were
strong enough to make a camera working (even a large reflex camera)
are completely unable to actuate a small numerical camera; if you
chose a model which accepts the LR6 (AA) or CO3 (AAA) cells, put
into refillable batteries of the same size, by choosing a good
capacity (1600 to 2400 mAh).
Batteries can replace cells but have only 1,25 volts duty tension
(1,42 max), comparing to 1,5
volts (1,65 max) for cells
;this lower tension can limit or make impossible to use
them replacing the cells, the more so as modern apparatuses are
designed not not to use the cells too much.
Explanation ;
if you have an apparatus which stops functioning when the cells make under
than 1,35 V each one, it will only function very little of time with the 1,
36 volts of the battery however full charged (it is almost its maximum).
Batteries loading
; a slow loading (example 6/12 H) must be preferred to the fast load (example
15mn/1 H), in fashion; it is more complete and take care of the batteries.
Advantages:the battery delivers its energy more regularly than the cell, its tension "remaining more constant.
The battery can deliver a current much more strong (amps) that a cell, with an equal capacity.
They will get running an apparatus greedy in intensity of current (amps), where a cell will collapse. A manufacturer announces3 times more power if not energy than alkaline cells
AA, for his battery of 1700 ah: Truth or not, my own tests show that they really have more energy.
Disadvantages;
while in stand by, the battery discharges more quickly than the cell.
A small accidental short-circuit can destroy it irremediably;
this short-circuit, not too much dangerous for a small capacity hereby quoted, get run big risks when the capacity is significant (battery of car).
If both its terminals plugs are accidentally connected, a battery of car can melt a wire, a key or a grip in a metal in
fusion explosion !
That could not occur with cells of egual capacity because the cell slows down the passage of significant
currents and heats a lot (it consumes in fact its own energy, one says that
it has an interior resistance).
Vivid generators or live inspired to.
It has been known for long many fish produce electrical current and therefore electric fields generally intended to
detection and defense. Most talented of them are Malpterure, a one
meter catfish of tropical Africa and gymnotusa, a one meter
flattened eel, which respectively can produce up to 350 volts and 600
volts. 600 volts, which cause a muscle tremor to humans, followed by a
painful numbness. As for the torpedo, its merely small 40 volt
are enough to dazzle or knock out its prey. These cases are exceptional by
their power output although electricity production by animals is not. We
also produce electrity for the functions of our nervous system and
muscles, on the basis of calcium ions. Electrodes that excite here and
there our muscles to exercise without effort, or those who make reacting
an area of the brain are testifying the process. As for our batteries, the
operating process of the gymnotus generator is based on the displacement
of ions by difference of concentration (sodium in this case) in about six
thousand cells housed in a large part of its long tail. Triggered by the
needs, pulses may accelerate up to tens of strokes a second. (Larousse
Encyclopedia).
Vivid electric générators.
In December 2007, a Japanese aquarium connected strings of his tree to a pool containing
an electric eel gymnotus. Metal plates attached to the ends of
the basin allow the fish to feed the bulbs. "Le Courrier International" in
January 2010. They do not say "she" was tired .. Research continues in
this area and U.S. researchers think they can soon produce batteries for
small electronic devices, like MP3. The micro-hydrogen fuel cell is also
in the running. Many promises can become tomorrow reality
Use reloading batteries in all cases
cells are quickly deads. Putting reloading
batteries in a clock or a bath room scale won't get you an appreciable
benefit because they can last several month or years.
but they can be interesting in a radio door chime,
a radio set with loud speakers, electronis camera or games. The reloading batteries now
a significant capacities, up to
2500 mAH, which is very interesting.
A manufacturer announces 3 times more energy than
alkaline cells AA, for his battery of 1700 ah: Truth or not, my
own tests show that they really have more energy.
- A
battery cuts its service suddenly. A radio set
powered with batteries do not
prevent and cut off without any warning, or very short one.
Example with a camcorder. The
battery lithium is marked 7,2 volts. It is the average operating voltage. At
the end of the load with the provided charger, one finds 8.25 volts. These
8.25 volts are falling to nearly 8 or a little less as soon as the apparatus
is switched on (7,92 in reading). Each
stop and restarting "kill"the battery (engines of positioning of
tape). Il is preferable not to cut it while waiting for another shot. As soon as the caméscope is cut, the battery
recover back in a few seconds or minutes
and one can make still a few seconds movie. That can depend on the batteries,
some begin again, others not. Better not
insisting too much. That can kill the battery pack.
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Batteries Ni MH1,2 volt duty. They reach nearly 1,4 volts once loaded.
They end duty at nearly 1 volt and do not are used. They risk total
destruction, what can occur while forgotting to swich off a torch that does
not lit anymore.
Usages of batteries.
- As all loading batteries, take care not to short circuit them because, at the contrary of regular batteries, they are able to deliver a very
strong intensity, that can possibly high damages (destruction, firing, explosion).
- A weak or cold battery can give again a little energy by letting it rest a few minutes and
by heating it under the arm or inside the palm.
- It seems that Lithium batteries do not appreciate low temperatures (below zero Celcius), at the opposite,
batteries Ni MH would not stand the temperatures over 50°.
Possibility to swich a battery for another reloadable, or another size.
One can think at replacing LR14 cells by AA (LR6) batteries 1700 with, 2500 Ah and more, by manufacturing adapters.
See photo.
For a small power, it can be useless to buy the large refillable models because it do not have more capacity than
AA (LR6). It is here about a razor for camp-site. What you need to do is find a tube to enlarge the diameter around the new battery, so
that it coild be positionned on the rifgt way. So, the receptacle of a AA is
obtained with a cartridge of hunting found in a forest.
I use also various tubes like electricity ones. In case such tubes do not suit well, one have to manufacture them with paperboard.
Depending of the battery size, can be also rising the problem of length, because both ends of the battery must be in contact with the back spring.
In this case, you perhaps can pull strongly , or on the spring to get it more long. If not possible, find another spring.
LIGHTING
Better to check the contacts while screwing on a little at a time.
Disadvantage: they are larger (one is accustomed to it).
1/ Halogenous lamps : a gas circulates inside and redeposits the vaporized metal of the filament. This phenomenon works only if
the temperature is high, that is to say variator to the max, at least at the
beginning (dim a little afterwards). If you use it always at a reduced power, the
filament will wear much more quickly. White light and lifespan are true values;
very useful as spots for giving lifeto a wall, a corner, an object, where regular bulbs do not allow such a
beam. But watch the consumption. With 20 Watts ones, you can set up several of
them ; fot reading 50 W can be necessary. Many halogenous lamps are used with an
indirect lighting and make 150 (rare), 300 or 500 Watts, i.e. the power of a
small radiator. Few people use them at full power and it is better to take a
mere 150 or 300 that one 500 half dimmed with the variator. If the white upsets
you, use traditional bulbs, more friendly !
2/ neon type lamps ; really economic? I did not make calculation with the purchase price but that must be true if they hold really the duration.
To leave lit a long time and not to play of the switch because lightings enormously goes up the consumption
and use prematurely it. Moreover, they need time to reach their level of normal lighting.
3/ flashlights ; check the bulb of your lamp. For a lamp with two 1,5 cells (3 volts), you may find it beneficial to put a bulb of 2,5 volts -
0,3 amps or 2,3 volts - 0,3 amps at magnifying glass. These ones offer most often the best result. That also depends on the reflectors, therefore a test is
to be made. One now finds bulbs supposed being more powerful (halogens and
others) but attention, they consume enormously and read straightforwardly 1,3
amps !! It is the case of the snake light of Black &... whose
reflectors too widened does not light... in spite of a frightening consumption (nearly
4,5 times more). Replace the bulb by a normal 2,5 volts - 0,3 A (amps) or one
2,3 v - 0,3 A with magnifying glass (American base, without screw); you will see
as well if not better and much longer. A bulb 2,3 Volts "will be boosted a
little" with the 3 volts of the cells (risk of breakdown), but that will be to
you much less expensive than the renewal of the cells.
4/ electric garlands ;
A/ There is no transformer (black block to put in the catch), each bulb receives a fraction of the total tension
of the sector (230 volts); bulbs are assembled in serie and it is thus necessary
to replace a bulb roasted by a bulb of the same model of garland (an even number
of bulbs, example 30 per line (wire). There are often several wires (lines)
twisted together, is 4 electric wire with that of the return to the catch). In this case,
the garland will aira 90 bulbs (three circuits of 30).
There is now frequently a
transformer, because the number of bulbs is high and the bulbs tiny (unremovable).
The transformer limits the tension (for example, 12 volts); in this case,
the bulbs are of type 12 volts and are assembled in parallel. See garlands.
Electrical current understanding
One can compare the electrical current with a river. the slope or the pressure pushes water. The larger
the slope (or pressure) is, the more the water flow can become
significant. In electricity, tension (voltage) has can be comparable
with the slope or the pressure of water: the tension "pushes" the
electrical current: the stronger the tension is, the more the flow of
electricity can increase. The width, the straightness of the river, the
presence of rocks, can slow down water. A new factor with thus
intervenes, the nature of the river. In electricity, it is the
resistance of the driver which slows down the electrical current (diameter
of the wire, nature of metal, aluminium, copper, money, gold). It is
measured in Ohms. It results from this, it is the witty remark! that
electricity "will run" better (intensity in amps), with equal "slope" (equal
voltage), if the resistance of the river is less large (the electric
driver is better and larger). One summarizes that by the basic formula
in electricity, U=R*i where the tension "U" is expressed in volts, R the
resistance expressed in ohms and i flow expressed in Amps. One can to
write formula thus i=U/R (intensity = tension divided by resistance)
which shows well that the flow (amps) also depends, as for the river, of
the slope and the bed of the river (resistance). It is proportional to
the tension and inversely proportional to resistance (divided). One can
also write in the form R=U/i (U divided by i): example for a bulb of
flashlight to two cells of 1,5 volts equipped with a bulb of 0,25 Amps:
R (Ohms) = U (3v)/0,25 (Amps) = 12 Ohms.
A condition must however be respected; the
contribution of water water (source) must be sufficient (stopping,
rain). If it is only one thin filament of water at the beginning, one
will do nothing with in spite of the slope. It is the same thing
in electricity, if the contribution of electricity (source) is
weak, a strong tension will not allow a large flow of current. It
is fundamental for including/understanding well: the tension does not
bring necessarily the power. Comparative example: the pressure
is strong with the tap but the hole of arrival or the pipe very small or
is stopped: one opens the tap and after a small jet, there is no more
that one thread of water (the pressure cannot be maintained). In
electricity, one can in the same way have a strong tension which, as
soon as one connects an apparatus above, breaks down. Example, a small
too small power supply unit 12 volts for the apparatus which one
connects above. It is necessary that the source can provide
without failure (to output) to maintain the pressure/tension and thus
the debit/intensity.
A generator of electrical current is represented here in the shape of
a hydraulic pump (left reinflated on the left drawing).
In the electricity case, the pump (generator), produces a
pressure of positive particules at the exit and negative for the return.
On the right-hand side, the narrowed part of the circuit slows more down
the current, it is the receiver (apparatus, electric tool, radiator,
engine.). This hydraulic model shows that (large) pipes (electric
conductors) opposes only a feeble resistance to the current.
Consequence? the diameter of the electric wires must be of a
diameter well adapted to the power of the receiver (apparatus). There
are usually wire of 0,75 - 1,5 - 2,5 mm in diameter. Take care
while buying them that they match the power they will be used to, or
they could heating ! a bigger diameter is necessary for the electric
cookers/oven (6 mm), protected by a 32 Amp fuse. Or the fuses
could blows, the wire heat, the plug and socket burn !
Résistance
interns of a generator: the bulb of the red
light of my bicycle does not light any more (one diode LED). By
measuring the cells, I find nothing any more but 1,42 volts with each
one. To check again, I place an ordinary bulb 2,5 volts at the poles of
one of the cells: it ignites slightly: an new mesure finds only
1,29 volts! From 1,6 volts at the beginning batteries fell to 1,42
volts without igniting any bulb, to 1,29 while igniting (one also says
"in load"). Why the tension fell down ? because the cells have an
interior resistance, and this one increases with the usage.
<>To check the good state of a battery, one must
measure it "in usage"<> that
is to say with a bulb ignited or an adapted resistance. There are
small cheap testers of cells in the trade which allow that.
The power of our river depends on
the flow, which is a volume (thus a mass) and a speed (cubic meters
per seconds). In electricity, the power is given by the formula
P=U*i (volts multiplied per amps), where P is the power
expressed in Watts, U "U" the tension expressed in volts and i the
flow expressed in Amps.
Can one have a weak tension (slope) and an intensity (flow)
very significant? yes if the source of electricity (battery, generator)
has good "reserves" of electricity and that the resistance of the driver
is very low. Example, the starter of your car only outputs a very strong
intensity under 12 volts. Can one have a very strong tension and a very
low flow? yes if the resistance of the driver is very large. Example,
the lighting of the tubes neon does not require - relatively - that a
low intensity under a strong tension, to ionize a gas inside the tube.
The strong tension is produced by a system with transformer starting
from the 230 volts.
Providing without failure: so that the tension of a
generator does not fall too much while working, it must be sufficiently
dimensioned and to have a low interior resistance. It is thus
characterized by the power which it can provide, and which will depend
on its charging voltage (in service) and on the intensity which one will
be able to get from it.
Example: how much
does the flat iron consume of 1000 Watts? one can modify the P=U*i
formula in i=P/U (i=P divided by U, it is similar); therefore, under 200
volts there is i=1000/230=4,34 amps
Remind ; when one measures the tension (voltage), the
apparatus should take only very little electrical current not to disturb
the measured current produces because one names "the source" or "generator"
(pile, sector, dynamo, alternator, solar panels.). The most delicate
measurement is that of the intensity because all the current must cross
the measuring apparatus without it being slowed down by its resistance.
Output. In the apparatuses other than the radiators, such as engines,
transformers, etc), this heat, inevitable, is not desirable because it
corresponds to a small lost power, which decreases the output of the
apparatus. By this loss, the transformed power collected at the exit is
a little lower than that applied to the entry. However, the electricals
appliance have all a good output, about 90 to 95 % or, compared more
with other types of machine (vapor (4%), petrol engine (40%), laser
(10%), lamp with incandescent 7,5%, the remainder leaves in heat).
Measuring, meters
;
If one measures
the no-load voltage of a cell LR6 1,5 volt
with an apparatus which consumes too much power, measurement will be
completely distorted because the source (battery) breaks down
immediately; worse, the battery can be damaged. The measuring apparatus
does not have to, or very little, take power on the source. The current
electronic multimeters are much righter than the mechanical apparatuses
(with mobile framework) because they not take their power on the source
but on their own cells they are equipped (there is amplification).
Thus, an electronic circuit, whose powers in circulation are very low,
will be measured with a very sensitive apparatus and not with an
apparatus intended to measure industrial current, like 230 volts!
This
concept is fundamental: conversely, if it is not protected, this very
sensitive apparatus will be destroyed by a too powerful circuit for him
(the sector 230 volts). Anemometers are sometimes destroyed bycyclones!
Types of measuring apparatus.
The tension (voltage), indicated by "U" and expressed in
volts "V"). the apparatus most usually used in electricity is
the voltmeter which measures a tension in volts. The intensity (flow),
known as also amperage, indicated by I and is expressed in Amp "i".
One measures it with an ammeter, which is in fact a kind electric
flowmeter. The higher the value in Ohm is, the more resistance to
the passage of the current is large. The resistance of a driver is
measured with an ohmmeter.
Watt, Volt (Volta), Amp and Ohm are the names of four physicists.
Remind; when one measures the tension (voltage),
the apparatus should take only very little electrical current not to
disturb the measured current produces because one names "the source" or
"generator" (battery, sector, dynamo, alternator, solar panels.). The
most delicate measurement is that of the intensity because all the
current must cross through the measuring apparatus without being slowed
down by its resistance.
Output. In the apparatuses other than the
radiators, such as engines, transformers, etc), the heat, inevitable, is
not desirable because it corresponds to a small lost of power, which
decreases the output of the apparatus. By this loss, the transformed
power collected at the exit is a little lower than that applied to the
entry. However, electrical appliances have a good output, about 90 to 95
% or more, compared with other types of machine (vapor (4%), petrol
engine (40%), laser (10%), lamp with incan
Electricity
power ; it comes from the lightning, the static
electricity (see above) or better for our comfort, from a
generator (pile, the invented first, battery, magneto,
dynamo); one naturally establishes an equivalence between
the mechanical or chemical energy and the electric power
which result from it. The current unit is the kilowatt-hour
(1000 Watts during one hour) which corresponds to a
generator (source of energy) which would deliver a current
of 10 amps (intensity of the current) during one hour with a
tension of 100 volts (tension of the current). One
summarizes that by the formula W = U (volts) * I (amps) * T
(time) or signs it * wants to say "to multiply"; to
include/understand these terms and the formula, imagine that
the current (I amps) is a flow, like that of a tap, more or
less significant and that the tension (V volts) is the
pressure of water on the outlet side of the tap (see water
flush ). The power is P (Watts) = U * I.
Practical
application; flashlight lamp.
Your uflashlight functions with
two cells of 1,5 volts, that you put one behind the other in
the lamp (it is said that they are in series, therefore
the whole deliver 3 volts); your bulb indicates 2,5 volts and 0,3 amps;
under 2,5 volts, it would have a power of P=U * I, that is
to say 0,75 Watts. It is nearly reality because the tension
on the outlet side of the two cells will drop rather quickly
under 3
volts (there are losses in the cells (which
heat a little) because of their internal resistance. If you
light during 15 mn, you will have spent 0,75 * 0,25 (1/4 of
hour) = 0,1875 kilow/h. One cannot know how long that will
last because the manufacturers are dumb on the capacity
(energy) their cells.
Electrical power,
vacuum power :
a vacuum cleaner of 1500 Watts has a power of
aspiration of 30 kPa: 30 kpa means 30 kilo-Pa either 30.000
Pascals, equalizes about to 30.000 divided by 9,81 = 3050 kg
per square meter, or
305 grams per square centimetre, or
still the equivalent of
a water column of 3,05 meters or 3
divided per 13.6 (density of mercury) =
225 millimetres (mm)
of mercury (Hg) or also
300 millibars (that's all !! ). It
is this aspiration (depression) that it is necessary to
compare. To finish, that returns to almost 1/3 of the
atmospheric pressure, which is worth in general on the sea
level 760 mm of mercury or 1013 millibars (thousandth of
bar). With all these equivalences, no manufacturer can more
mislead you.
Advice
: best is to note prices and
duration of the cells to compare them. The good bargains are
often for the salesman. Flashlight ; check the bulb of your
lamp. For a lamp with two cells (3 volts), you may find it
beneficial to put a bulb of 2,5 volts - 0,3 amps or 2,2/2,3
volts - 0,3 amps at magnifying glass (the bulb comprises a
round nose). It is with these that the result is often the
best. That also depends on the reflectors, therefore test
them. One now finds bulbs supposed being more powerful
(halogens) but beware, they consumes enormously and reads
1,3 amps !! . It is the case of the Black &...'s snake
light of whose reflectors too wide does not lit... in spite
of a frightening consumption (nearly 4,5 times more than a
regular one). Replace the bulb by one 2,5 (volts) - 0,3 A
(amps) or one 2,2/2,3 v - 0,3 A with magnifying glass; you
will see better and much longer.
ELECTRIC DANGERS
One speaks here about the
230 volts main current which reach really 230 to 240 volts. This current can be very dangerous. Not to touch the stripped parts of the electricals appliance connected on the sector.
The current 12 volts is absolutely inoffensive. That can sting a little, that's all.
An isolated transformer 230/230 - that cut the return of the current by the ground is mandatory in the bath room for the electric shavers or hair dryer. Certain hotels are equipped with it).The 12 volts can be obligatory sometimes certain industrial wet places.
The material: The electric dangers most usual are in the house.
For the electric installation of a bathroom, there are restrictions which determine volumes
in which no taken of current must be posed. Lastly, do not forget that the
bath-tub is almost always mortal with a hair dryer or when one touch a
defective luminous bracket (they must be put at the ground if they are in metal). Even the ringing of the telephone formerly killed there
in it. More usually, the defective and not protected sockets, the cables in bad
condition, extension cords, the coppered casings of the lamps, adaptor and
extension sockets, constitute many weak
points.
Conditions the way in which one seizes the
defective element determines the passage or
not current by the heart. Thus, staning up on a stool to replace an electric
bulb, the arms tended in the air, there is risk of serious or fatal
electrocution if an electric wire touches the casing inside. Put on gloves,
or wrap the casing of rags or to shut off the
main current, which is always better. moisture and bare foot increases considerably the risk,
the tiling also moisture can come from the moistness of the hands and the
feet, especially if the skin is fine (absence of callosities). Or of the
ground, (interior and outside).If your washing machine overflows on
the ground, first of all go straight to cut the the current at the meter and do not try to
switch off at the machin! in the
garden, also think of the electric mower when the cable is
wet.
Electrical connectors and power supply units (stations, etc);
think to check them from time to time : touching them, they must not heat, even without anything of connected.
If they do, they can melt and cause a short-circuit.
this is true for extensions cords, socket extenxion and for the fuses
panel. For a cut wire or an extension cord, one very often makes a connection "as
one can". Ends are twisted tight, but should be welded with
tin, then separately coated
with an adhesive tape if not be plugged into a standard screwed box. On
line, it is recommended to cut the two bits to lengths
different so that two connections do not fall opposite one the other. One surrounds the whole of another ribbon. One can also drown
the connection thus carried out in adhesive cement, silicone for joint of
bathrooms (cartouches Rubson kind), of plastic to be softened in hot water
or moulded in a stuck of cast paraffin
(for preserved jam).
In nature; do not approach you the electric pylons if wire
fell to ground. A mere step on the ground can electrocute you
when you are within a few meters from the wire! how? by the tension which results
between your two feet: it is called "the tension of step". By planting two
metal stakes connected to a bulb, it would light. Do not urinate either
close to the powerlines because the urine, salted is very conducting and
there are always escapes by the pillars with high and very high voltages.
The consequence of electrocution; from 10 to 15 my, tetanization (paralysis)
of the muscles of the arm and hand, possibility of surface burns; from 25
to 35 my, total tetanization of the members and rib cage (one does not
breathe any more). The heart does not resist more than 50 my, but many
damage can occur front. There is also an effect of electrolysis, i.e.
decomposition of the matter, therefore fabrics of the body. The most
serious effects, if one is still in life, are due to the destruction of
the nerves by which the current goes up. Saved being is believed but the
members (arm.) remain paralysed and the gangrene starts to develop in the
member, who should then be cut quickly. This effect is in general little
known, because it hardly touches but the casualties by high voltage,
working or falling on these lines. The danger augment with the tension?
yes and not. It rescapés there of the very high voltages because there is
then a skin effect similar to that which occurs with high frequency
currents: the current with tendency to desert the center from the driver
to circulate only with the periphery. That can save, but it is not there
not to better count, the more so as there can be serious burns of the
skin. Another precaution to be taken, most difficult, not to approach, nor
to touch an electrocuted person if it is still in the critical zone or is
not disengaged from the wire, because you are likely to leave there your
life without being able for saving it as much. If the person can be
touched, one proceeds as for the unconscious victims and who do not
breathe any more: position on the side, to leave the language, to make the
coordinated artificial respiration (stops with mouth alternated with
strong pressures on the chest).
Danger of the electric fields; the water
jets create electrostatic fields which can become significant, for example
for industrial washing. It is thus necessary to be secured some because
there is electric risk of discharge. Electrostatic danger; the sparks due
to the electrostatic loads have a weak energy but can cause large damage;
Many operations require their precondition neutralization. The supply of
the planes in flight is preceded by the discharge of the apparatuses. The
grains and the powders are to be feared, in particular during their
storage. The explosion of silos is not so rare.
Résistances
Electric resistance act as a brake
on the electric current, like the bed and the banks of a river slow down the
stream. Both the electric generator
itself and the apparatus (receiver) have a résistance. Whatever the size
the wire diameter is, and short the
length of the electric wire, there is always a little resistant.
One can obtain a null resistance (0 ohm) by soaking
the wire in a very cold fluid (minus 270 degrees !! brrr); in this case,
the resistance of the wire would become null. It is not
theoretical and experiments take place by exploiting this possibility.
Resistance becoming null means that one fear of making circulate a current
which, once establishes, does not require any energy to be maintained. One
believes to dream, but one tries industrially to use this principle, in
particular for the levitation of vehicles (trains) on frozen electric coils
"archi frozen" distributed throughout the rails. Freezing and very short wires are mandatory inside the most powerfull
computers.
Connecting
resistances. Here are three schemes which make it possible to
understand how one can group resistances, for example to adapt the receiver
(here loudspeakers of an amplifier) so adapting them to the generator (the
amplifier Hi Fi). Each loudspeaker of the speaker has a value of 8
ohms.
The exit of the amplifier can vary from 4 to 16 ohms. To
obtain the best power (output, adaptation), the resistance, which one names
impedance in AC current, must be the same one on the outlet side of the
amplifier as at the entry of the loudspeakers.
The first assembly shows two loudspeakers assembled in
parallel : resistance will be divided by two, that is to say 4 ohms.
The second assembly shows two loudspeakers assembled in
series: resistance will be multiplied by two, that is to say 16 ohms.
The third assembly shows a mixture of both, parallel
series: divided then multiplied as in the preceding cases, resistance totals
8 ohms.
If the exit of the amplifier is of 8 ohms, the first
assembly is likely to force its power while wanting "to draw too much",
while the second assembly "will not draw enough" and either the best effect
will not obtain. It is clear that only one loudspeaker of 8 ohms is adapted
in this case. Moderate: in a high speaker, a membrane follows the
displacement of a reel of wire placed in a circular magnet. So the electric
wire has a resistance and also a self-inductive effect of with the reel. It
is said that it has a "impedance". This one increases the value of pure
resistance, but that depends on the frequency of the current to see "AC
current"
Alternating current
(AC)
The alternating current is easier to produce because the alternator
is simpler mechanically than the dynamo, reserved for the D.C (continuous/direct
current). Moreover, its transformation is made possible by double coils,
named transformers, which raise or lower at will the voltages; that with an
excellent output (low losses), at a rather low cost. One thus raises the
voltage to transport the current because a high voltage limits the intensity
at equal power (see above, electric power), and by the fact, makes it
possible to reduce the diameter of copper wire on the lines.
On
the right hand drawing, the current comes from the A
hole of the socket to the B one, then comes from the
B hole to the A
one. And that 50 times per second.
The AC current is represented by the
form of a sinusoid, that is to say a curve which undulates like a snake or
the whorls of a spring. For as much, the electrical current does not jump up
and down as one could believe it, but it changes actually of direction 50 times a
second in Europe, 60 times in the USA. That really means that the current
arrives by the right hole of the catch, grows then vanishes and returns by
its left hole! that 50 times a second. As it changes constantly and takes
various values between these moments, one must define an average
current to study his effects. In France, the value of 230 volts means it has
the quality of a 230 volts D.C.l
(the real value is 227)
If
the 230 volt is an average value representing a D.C. current of this value,
does that mean that the tension (voltage) at the socket/outlet passes by a
stronger value? yes, this maximum value "reaches a peak" 50 times a second
at 230 Volts x 1,414 = 311 volts
(reality should be 227x1,414 = 320v). Just as it also passes by zero volts.
With the AC current, two new effectscomes, the capacity and the self-inductance. One, the capacity it is like a
temporary stocking that comes as a leak between the two wires. Two, a coil
provides an additional resistance to the establishment of the current.
A 5 Ohmsresistance conductor with a Direct Current (D.C). can become 150 Ohms
with an A.C. if this resistance is made, for example, with a fine
copper wire wound around a magnetic core.
Effects of the self-inductance (coil).
The igniter coil of your car engine, that which makes the sparks on the
ignition plugs, is a coil which presents an effect of significant
self-induction. That coil however receive a mere 12 volts D.C., but in the
form of impulses (that turn it out as a kind of half AC current because it
is variable but does not change direction). The current is braked at the
time it is switched on by the coil, but once established, when it is very
quickly cut, the coil gives back an extra current of rupture of higher
voltage. Supplemented by the second winding which raises the voltage still
more, one thus obtains 15.000 to 20.000 volts with the 12 volts of the
battery. It is sufficient to start a spark between the electrodes of the
plugs, spaced of a small millimetre. With a coil (winds of electric wire),
one can thus receive, in spite of a weak D.C., a strong discharge of current
at the time of the cutting out.
The coil delays both the establishment and the cutting, because the
current incline to be maintained. It produces an extra current of
rupture if one cuts off its electrical current vey quickly. If it
gradually is reduced, before changing direction, as it is the case in AC
current, the coil tends simply to prolong the current which was established.
It is said that it introduces a delay (lag, dephasing) of the current
(intensity) into the circuit, compared to the moments of establishment and
suppression of the voltage.
The shift between the tension
and the intensity can be such as the tension is to the maximum when the
intensity is at the mean (zero). In this case, one has electrical current
well, but the product U * I is null and the power too. There would be thus
current free. This is why EDF imposes a limit on the shift (dephasing), for
industrial facilities.
The current wich is composed by the voltage and the intensity running along
together (same time) is said "active", because it correspond to a certain
quantity of Watts one can use and is to be paid.
Electronic circuits have four kind of
elements, the transistors (and alike), pure resistances (small cylinders
with coloured bands), the capacities (various forms often punts, with
coloured bands of which the chemical ones of strong capacity under aluminium
tubes), and the coils, sometimes protected under small aluminium cubes or
resembling small transformers.
Sometimes the connection cords of the radio and
electronic apparatuses, have close to the plug a kind of bulge: it is the
wire which "is wound" around a magnetic core. Why? by its effect of self,
this coil reel prevents the stray currents of high frequency from disturbing
the apparatus (those which would arrive by the main, or else origin).
Because the more the current has a raised
frequency, the more one self-service slows down it (weakens it).
One use many currents of high frequency radio and general electronics, they
are to be protected from others, unwished.
The resistance of a circuit made up of
resistance, capacities and coils is called "impedance" and the resistance
opposed by a coil alone (*) is more precisely called "reluctance". What
marks its reluctant character well.! In fact, the coil has
always a resistance too, because to make a coil, one needs electric wire
which is always a little resistant. One could obtain a pure coil by soaking
the coil in a very cold fluid, with less 273 degrees!! brrr! in this case,
the resistance of the wire becomes null.
Effects of the capacity. A capacity, called more
usually condensing, is obtained by rolling up a sandwich made up of two
conducting sheets between which one places another insulating fone. A gel
soaks the whole. By applying a tension between the two conducting sheets,
one of them develop a
+
on its surface and the other a
-
, the whole preserving a certain quantity of static electricity which one
can retrieve by discharging it. The condenser delays the establishment of
the current during its loading time. So it lag/delay the establishment of
the current. It is said that it introduces a lag (dephasing) current
compared to the moments of establishment and suppression of this one.
At the contrary of the self/coil, it is the tension which is this late on
the intensity.
"Big" condensers (it is
relative), are also used as electric reserve of power, in particular for the
our electronic instrument supplies, because they make it possible to control
a little the current while providing some at the time of "blows" of the
request of the receiver. They are of course electronic instruments and EDF
company cannot store electrical current thus. The storage of energy remains a
problem because one cannot store electrical current in great quantity. Only
"Geo Trouvetout" can do it by collecting the energy of the flashes! The only
currently known means is to use batteries, but even in a telephone exchange,
to take an example, that remains enough limited.
Nature of the electrical current
The electric generator, a cell for instance, exerts a pressure at
the positive exit
+
which "pushes" free particles contained in the atoms of the
metal (copper generally), gradually, to go joining the other pole, the negative
one
- this scuffle within metal, a
little disordered, produces a kind of wave which will form the electrical
current.But nobody saw it ! By looking at the left hand figure, one
understands that the positive
+
and negative particles
- ,
attract oneself mutually ! look
at as these pretty young ladies precipitating to reach all these machos. It is
not any more of the electrical current, it is the Paradise.
Let us enlarge a little the wire : inside, there are atoms
(see physique 1)
these atoms are a little different in a conducting body and an insulator. In a
conducting body (metal), there are many atoms which have lost one or several
electrons (due to shocks) and consequently become positive. The lost electrons
wander about while combining sometimes with other positive atoms, whereas others
escape. In short, one does not know really what occurs. One could say that the
driver
"is ionized" because it contains particles (ions) positive and negative,
but this term is mainly used for the air.
In an insulator, atoms are much more "rigid" and retain their
electrons firmly.
The tension has thus much sorrow to make move the
electrons in spite of its forces+
and
-
gathered each side. Excepted
if they increase in strong proportions, becoming very threatening, then far
too strong for the insulator which then ionizes and cracks, bored by
the current.
In a semiconductor (transistor),
a very fine silicon slice "was doped", not with the EPO or creatin, but one
insufflated inside microscopic puffs of ions under the gas nature. The whole
remains insulating until one applies to him a current. At this time, the
power can pass through proportionally. A transistor thus functions a little
like a tap. Tiny, It has three electrodes (three electric wire. Two are on
both sides of the silicon slice "to make pressure" on each side. In the
medium, within the section, the third electrode is placed. It is through
this one that one will apply a variable current of command, which will let
pass or not the current between the two opposite electrodes. The third
electrode thus acts like a tap, which one can turn of a blow or gradually.
An integrated circuit
resemble a tablet or a tiny a black seed
(credit card) around which enter lots of electric wires (open an electronic
instrument, or slit out the the tiny patch which is on an out-of-dated
credit card and you will see that). There are no transistors with full of
wires, because all is engraved inside the matter at a scale we can't catch
up. It is a true city of hundreds, thousands or
tens of thousands of transistors, and much more in the future, with their resistances, their capacities (condensers),
their coils. Their design requires a tower to photograph the immense drawing
which the machines will reproduce on a tiny scale that we know. What we can
see (numerous wires) are only the way in and out of the city ! Another
world.
Static electricity, electric fields
The odd Scotch
tape
(which
one can put where one wishes) ; the adhesive tape Scotch tape " is
electrified " when unrolling it because it loses particles
(electrons) on both sides by pulling it up ; so it is eager
to quickly find the particles which miss for its own balance
and for that tendency to " jerk" and to stick itself
anywhere, nearly uncontrollable (point out you to the
reinforcement of the foldings of road maps, it is always at
side). One can improve appreciably this asset with my
do-it-yourself item, for small lengths; see " recipes of
do-it-yourself ". Sparks with door handles,
underwear.
You
surely do have already got some sparks through the handle of
your car and for the worst case between lips when kissing
someone while grasping the handle door car; the same for
door handle in a flat, specially if the ground is covered
with a carpeting. Underwear or synthetics jumper are also
well known for this little assets.
Ionization of clouds.
It would be from now
on admitted that the lightenings
clouds to ground or inside
clouds themselves would be
due to a strongly ionization
(*)
of the top of the clouds by cosmic rays.
(*)
ionization ; loss of an electron in an atom following a shock.
The
lightning
of which the
main discharge goes up towards
the sky... after a progression of small discharges,
on several levels, called precursor, made the connection in
the direction cloud-ground. The whole process lasts only
some tenth of thousandth of seconds (milliseconds). The
lightning allows to understand the problem of energy and
power, which is always a little delicate: well, , couldn't
we store the lightning power, thought probably Benjamin
Franklin, just like we think ourselves too ! yes, but first
of all, we cannot store it and then,
it does not represent
much energy: the whole amount of the flashes recovered
in France would not exceed 20 Méga Watts (20 million
Watts).. E). A nuclear thermal power station produces 1000
megawatts).
And with all
the wires and installations necessarily, better forget it.
On
the other hand, the power is considerable. How to explain that
? he well,
only the duration intervenes.
A small energy
spent in a very short time gives a strong
power
(but of
course which does not last ! and if it does not last, one
cannot make great work with. Examples : the tornado (winds
with more than 500 km per hour) ; the man breaking bricks or
wooden planks (the blow is so quick (sharp) that the
material breaks because the molecules do not have got time
to organised resistance themselves (is it alive ? that it is
a real question). The
lightening acts in some millionth of second during which it
breaks all..
Electric fields, lightenings.Per stormy
weather, under a cumulonimbus trailing its base with 2 or 3 km of the ground,
the electric field can reach tens of million volts in fact, at a rate of
12.000 to 20.000 volts per meter of atmosphere. Not astonishing that one
feels electrified! These tensions increase further until the million by
volts per meter, value which ionizes the air (the atoms lose their electrons
(negative) which becomes free, the atom itself become then positive. At
this time the discharges (flashes) are déclanchent, producing during some
thousandth of second only, the currents of several tens of thousands of amps
and exceptionally, 100.000 amps. The power can be then very destroying. By
beautiful good weather, an electric field exists naturally in the atmosphere
by good weather and we bathe inside at a rate of a hundred volts per meter
height (such an amount of worse for the large ones!). Under the shower, the
water jet creates of it one of 800 volts/meter! what attracts the curtain
because one is electrified. The discharges which one sees ramifying and
hopping in transparent balls, fires of St Elme, brushes, luminous halations,
gleams are due to electric fields.
An electric field exists naturally in the
atmosphere by good weather and we bathe inside at a rate of a hundred volts
per meter in height (such an amount of worse for the large ones!). Under the
shower, the water jet creates of it one of 800 volts/meter ! what attracts
the curtain because one is electrified. The discharges which one sees
ramifying and hopping in transparent balls, fires of St Elme, brushes,
luminous halations, gleams are due to electric fields.
Fixing electric breakdown, see electricity repair.
- Wires continuity tester (only with unplugged appliances):
To check the electric cord of a domestic iron, it is necessary to make a small gear with a battery set and a suitable bulb (read here "ampoule") 3 volts for exemple (two 1,5 batteries)
This picture shows the assembly. You can improve the system by fixing (screw..) a "aligator" clamp at both wires ends.
- main power (115 or 230 v) current tester (on an engine, contactor, transformer); prepare an assembly with a flexible electric
wire, a casing of small lamp of refrigerator or sewing
machine and its bulb (12/ 15 Watts). Strip the end of the
two electric conductors and fix each one of them on a stick (with
adhesive tape). A grip "crocodile" can be screwed or welded
onto one tip of wire or both. It is recommended to wrap them
with a an adhesive tape to insulate them. To check the
presence of electrical current, grip the two wires on those
of the engine (it can y have a third ground wire called
"ground', most often green and yellow, connected to the
frame or a metal part; this does not have a current.
Tip of "pro"
: to test the presence of an electrical current at the end
of two wire moulded in a connector (terminal), that is to say, inaccessible, prick a dressmaker needle with small coloured round head or a safety pin
(according to the section of the wire),
in the middle of each electric wire, so reaching the copper.
The wire of the tester will be bond,
using a crocodile clip of electrician. With the main 240 volts,
warning !, shut
off the power during the preparations,
put on plastic gloves and do not work on wet ground
; check that the wire of the tester or pins are not in contact each
other. When the current is put on back, the lamp must ignites and the
engine starts (pump or another gear). If the lamp only ignites without
another effect, the gear is faulty and not the arrival of the current.
(bas)
Connecting
resistances. Here are three schemes which make it possible to
understand how one can group resistances, for example to adapt the receiver
(here loudspeakers of an amplifier) so adapting them to the generator (the
amplifier Hi Fi). Each loudspeaker of the speaker has a value of 8
ohms.
