The difference between connecting the negative wire to the frame or to the battery?

Question

Electronics

When a negative wire is thrown onto the body of a consumer, it turns out that electrons run throughout the body and this creates an additional. resistance?

Previously, the sensors had only 1 wire, and the mass went through the engine and then through the braid to the battery, I think this is a bad way, because if something rots somewhere, the sensor may not work correctly and its replacement will not help.

It is better to make separate chains + and -, as it is now done.

Answer 1

When a negative wire is thrown onto the body of a consumer, it turns out that electrons run throughout the body and this creates an additional. resistance?

I would not like to go into deep physics, but I have to. An electric field is distributed over the body (more precisely, over all metal parts connected to it), climbing into all corners, and electrons choose their path in a rather peculiar and not very definite way. They definitely do not "run" along the far ends of the body until these ends do not end with anything conductive. For them to run , the circuit must be closed, i.e. represent a ring.

Previously, the sensors had only 1 wire, and the mass went through the engine and then through the braid to the battery, I think this is a bad way, because if something rots somewhere, the sensor may not work correctly and its replacement will not help.

This does reduce reliability, but car designers need to consider more than just reliability. The use of mass as one of the wires of the on-board electrical network makes this network several times cheaper. And reliability is reduced only with poor care of the owner of his car.

It is better to make separate chains + and -, as it is now done.

I am not a motorist, and I don’t know how this is done now in automotive technology, but I know that not using the mass as one of the main wires of the on-board network is practiced in rocket technology. For rocket scientists, the issue of cost does not dominate, but reliability is very important to them. In addition, it is important for them to control the integrity of the wiring and the reliability of the insulation, and separating the case from the network makes this possible by very simple means.

Answer 2

this creates an extra resistance?

Yes, like any other wire. If the current is relatively small (not the starter), then the drop will be small.

through the scythe to the battery, I think this is a bad way, because if something rots somewhere,

What and where? If the "braid" rots, the engine will not start. Or will the whole engine rot?

Answer 3

Vice versa.
The cross section of the body is much higher than the cross section of one wire, so the use of a separate negative wire is harmful, the voltage drop will be higher along the wire.
As for reliability, it is also an incorrect assumption, the probability of damage to two wires is higher than one.
The negative wire is bolted to the case with a thick wire, the probability of its decay is almost zero.
Therefore, using the body as a negative wire increases reliability, there are fewer wires that can be damaged.
It also removes the problem of zero potential difference, in any place of the body the zero potential of the sensor will be the same, and if you drag your own negative wire to each sensor, then the zero potential will be proportional to the length of the wire.
For some sensors, the minus comes from the control unit to which the sensor is connected, there are also reasons for this.

Answer 4

There is no significant difference, except for the reduction in the cost of the production of components and the assembly of cars as a whole.
And as for the bad mass, the negative wire on the sensor itself can oxidize over time.