I’m trying to understand what’s happening in this circuit:

I------------------T1 (+333V)
I                 I
I                 R1(10K)
(pos)             I
1000V             I------------gnd (0V)
(neg)             I
I                 R2(10K)
I                 I
I                 IT2(-333V)
I                 I
I                 R3(10K)
I                 I
I-----------------IT3 (-666.7V)

I am learning basic DC theory from reading and sometimes I come across something I’d like to ask a question about, so:

  1. In the above circuit, without the ground, the voltage across all components would begin at 10V and finish at 0V. By adding a ground, I’m basically saying “here is 0V” and everything gets redefined in reference to that point and I end up with a 10 volt circuit with +3.33 as it’s highest voltage and -6.667 as it’s lowest.

  2. The electrons could care less, they still flow from the anode to the cathode of the battery under normal conditions, going from the highest potential to the lowest.

  3. This example was only used to demonstrate voltage dividers. It revolved around worker protection present in aluminum processing. Each machine is in series and mobile grounds are used nearest the machine a worker is using. I assume that this allows the worker to have the least exposure to electrical shock as they are also at ground potential?

I actually think working though these questions has cleared everything up, but please, comment on anything I got wrong.

Also, sorry about the crappy drawing, the autowrap in this editor really made things tough to format

Thanks!

  • litchralee@sh.itjust.worksEnglish
    10·
    10 months ago

    Before getting to the meat of the question, I think it will be instructive to clarify on what exactly a voltage is. Voltage is the difference in electrical potential. That is, it is always a relative measurement, taken between two points. Colloquially, you’ll hear engineers and electricians say things like “this wire is at 12v”, but they’re implying a specific reference point. There must always be two points to take a measurement; a multimeter must always have two leads.

    Often, that reference point is “ground” (aka GND, aka protective earth, aka COM) but the choice of designating a particular point as ground is always arbitrary. Even the physical soil of the earth is not at the same voltage level all over, which means a ground rod is only a valid reference within a certain proximate area. Instead, ground is often chosen by whatever is most convenient and reaches everything that needs it.

    But as you’ve found, having a ground reference is not mandatory for electricity to flow in a circuit. Instead, a ground connection serves ancillary goals, like personnel or equipment safety, or avoidance of objectionable currents.

    Comparing floating and grounded circuits, a single loose wire in a floating circuit will not cause a diversion of current to somewhere, because a second wire would need to be the return path. With two loose wires, there can be a second loop for current to flow. A grounded circuit intentionally ties some part of the existing circuit to ground, meaning you are now just one loose wire away from a possible diversion of energy, which could be fatal.

    This sounds like grounded circuits would be bad, and would imply that grounding the aluminum conveyor belts in your example would be insane. But this is actually the personnel safety from earlier, if we add the right protective devices to the circuit: a circuit breaker, fuse, a GFCI, or some combination. Those devices will cut out the power source upon a fault condition, and they require a sturdy ground connection to operate effectively. We improve overall safety by having protective devices, and having a robust ground connection.

    Finally, I want to offer a piece of advice as you proceed in your studies. The rule that “electricity wants to return to ground” is hogwash. It’s so hideously flawed compared to the true rule, which is universally valid: electricity returns to its source, in inverse proportion to resistance