Mass (electricity)

In a Electrical circuit, the branch of reference of the electric potential is called the mass . In the large majority of the cases in electricity the potential of this branch is of 0 volt.

In certain circuits, it is frequent to connect one of both poles (generally the negative pole) of the circuit to the carcass of object (car, etc).

Thanks to this, it is enough to a Electric wire to feed a consumer of current (lamp, etc), the return of the current being done by the carcass. It is said that the object is put at the mass.

It happens that the switch which orders, for example, a bulb, makes only one simple ground connection. In this case, the bulb is well provided with two wire and the switch of only one.

Breakdowns

A ground connection defective is a cause of frequent breakdown, because it happens that the body is rusted at the contact point, or that the various parts of the carcass communicate badly between them.

When the ground connection of a group of bulbs (block rear light/indicator of Vehicle, for example) is not done, each bulb seeks to make its return by the other bulb.

In this case, when the car brakes, that slightly lights fire stop and the indicator simultaneously.

Definitions

One can give at least three definitions independent of the mass in electricity or an electronics (or in CEM):

Théorico-philosophical : “The mass, reference of potential absolute, is the potential resulting from all the loads which populate the universe. ” This definition, which resembles during electric of the principle of Mach, is subjacent in the mathematical theory of static electricity (for example, in the definition of the concept of “capacity”). It is about a concept:

* local, depend on the endoit where one is,

* static, not taking account of the electromagnetic propagation.

Although little used, it is a good didactic support, for example to apprehend the concept of “common mode” in Historico-technological CEM…

: “The mass is a conducting mechanical structure, which is used, in addition to its mechanical functions, to be used as reference " physique" with certain signals electric, and/or to ensure an electromagnetic shielding. ” It is the carossery of the car, the carligue of the plane. Or the frame out of tin plate being used as support with the tubes radios of my station of TSF, frames on which are brazed all the drivers to be connected to the “zero volts”.

* it acts of an approximate concept (resistance can be low, but never zero) and local (there is not “mass” in high frequencies, only of the mirrors, antennas and diffractions… in any rigor, it is besides no either potential),

* in the case of several overlapping structures (a car radio and a GPS in a car on a truck in a boat…), to define “the” mass requires a great flexibility of adaptation to the context.

It does not remain about it less than this definition, used with precautions and without illusions on its limits, is most productive, in terms of practical utility.

Empirico-egocentric person : “The mass, it is the place where I connected the black wire of my voltmeter. Perhaps but I will change it place presently. ”

< polémique> The replacement of the frames of the time of the radio operator tubes by printed circuits caused a “loss of landmarks” in a population of inclined electronics specialists to regard “suppression” as a kind of sorcery based on ritual practices out of ordinary physics. It thus happened that one lends to the mass (or the ground) of the miraculous properties. However, a “mass”, in a printed circuit, it is nothing any more but one track or plan like the others, except for the name. And, to escape the parasites from the others, best is to have “its mass with oneself” (or “its ground with oneself”). Or, at least, it is what certain imaginent.< /polémique>

Thus one saw flowering of the terms such as:

*masse “logical”,

*masse “analogical”,

*masse “clean”,

*masse “video”, etc, etc

correspondent with variable potentials the ones compared to the others, the connections (conductive, capacitive or radiative) being able to be the seat of intense exchanges of signals.

At this stage, the concept of mass, which is never, in any event, that a support with the reflection, is more harmful than useful.

See too

electric Ground

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