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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. 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.
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). |
Advantages:
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).
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).
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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. |
- As all loading batteries, - 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.
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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 :
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4/ electric garlands ;
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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.
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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). 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! 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. 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
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| 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. |
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ELECTRIC DANGERS One speaks here about the
230 volts main current which reach really 230 to 240 volts. This current can be very dangerous.
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).
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. |
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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. 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" |
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Alternating current (AC)
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.
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 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. 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. 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.
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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. |
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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 ". 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). 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. |
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Fixing electric breakdown, see electricity repair.
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. You can buy a tester much more sophisticated (multimeter). See above on this subject, "measures and measuring apparatus". |
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.
