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| Talk me through this simple circuit? |
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| timelessbeing:
--- Quote from: Mr D on June 05, 2019, 07:20:38 pm ---the two circuits are equivalent --- End quote --- Yes --- Quote from: Mr D on June 05, 2019, 07:20:38 pm ---the choice to place the grounds where they are is completely arbitrary? --- End quote --- In this particular circuit, functionally it is arbitrary where you put ground. In AC and RF circuits, not so much. You can read about the concept of the "ground plane". As was explained, we do have conventions about where we put ground. Not to mention that thoughtful choice of ground location can make calculations easier. --- Quote from: Mr D on June 05, 2019, 07:20:38 pm ---........and in fact no ground need even be indicated in the diagram (as long as the ground symbols are replaced with a wire)? --- End quote --- In this instance yes. In other situations connecting high voltage to chassis ground can be lethal. |
| Mr D:
Thanks, we're now getting close to it being straight in my head. But still just one more thing: --- Quote from: timelessbeing on June 05, 2019, 07:45:06 pm --- --- Quote from: Mr D on June 05, 2019, 07:20:38 pm ---the choice to place the grounds where they are is completely arbitrary? --- End quote --- In this particular circuit, functionally it is arbitrary where you put ground. In AC and RF circuits, not so much. You can read about the concept of the "ground plane". As was explained, we do have conventions about where we put ground. Not to mention that thoughtful choice of ground location can make calculations easier. --- End quote --- Are you saying that in intergalactic space where a robot had to assemble a circuit from a diagram, some circuits (AA, RF?) wouldn't work in the same way if the ground symbols were replaced with a wires leading to a common wire, and some other bunch of nodes that lead to a common wire in the circuit was designated as ground? So, in the way i indicated in my two last pix? This is the nub of what i'm trying to get at: when there's no observer to reason about it, that ground as indicated on a diagram, is completely arbitrary in any closed, not actually physically grounded circuit! |
| timelessbeing:
Yes, that's what I said and I told you where you can read about it. https://en.wikipedia.org/wiki/Ground_plane |
| Mr D:
OK, that's a special case where the ground is more than a wire, it has some specific physical property required for the circuit to work. So anyway, apart from that, i guess the answer to my last question was "no"!. Thanks all for your patience, i'm going to move on now, but i'll be back soon with some infuriating questions about op amps! |O |
| RandallMcRee:
--- Quote from: Mr D on June 05, 2019, 08:02:08 pm ---Thanks, we're now getting close to it being straight in my head. But still just one more thing: --- Quote from: timelessbeing on June 05, 2019, 07:45:06 pm --- --- Quote from: Mr D on June 05, 2019, 07:20:38 pm ---the choice to place the grounds where they are is completely arbitrary? --- End quote --- In this particular circuit, functionally it is arbitrary where you put ground. In AC and RF circuits, not so much. You can read about the concept of the "ground plane". As was explained, we do have conventions about where we put ground. Not to mention that thoughtful choice of ground location can make calculations easier. --- End quote --- Are you saying that in intergalactic space where a robot had to assemble a circuit from a diagram, some circuits (AA, RF?) wouldn't work in the same way if the ground symbols were replaced with a wires leading to a common wire, and some other bunch of nodes that lead to a common wire in the circuit was designated as ground? So, in the way i indicated in my two last pix? This is the nub of what i'm trying to get at: that ground as indicated on a diagram, is completely arbitrary in any closed, not actually physically grounded circuit! --- End quote --- Ok, Ground point is not completely arbitrary in any real circuit. It is intended to be the point at zero volt potential. This is important when you are actually going to connect one circuit to another (think: one piece of equipment to another). Even in intergalactic space this must be done non-arbitrarily. Also, in any analog circuit using a dual power supply (e.g. +-15volts) the ground is almost always chosen as the zero volt point at equal potential to the positive and negative supply because this maximizes various specifications, e.g. for an operational amplifier CMRR, voltage swing, etc. etc. It will also become important in intergalactic space when one arbitrary circuit is grasped with one hand and the other grasps another arbitrary circuit at a potential difference of more than 40 volts. Perhaps. |
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