Connecting two circuits with a single conductor

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Discussion Overview

The discussion revolves around the effects of connecting two independent electrical circuits at arbitrary voltages using a single conductor. It explores the implications for current and voltage in both circuits upon connection, considering various conditions such as potential differences and grounding.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that initially, there would be no current between the circuits as they would attempt to equalize potential at the connection points.
  • Another participant indicates that the specifics of the circuits will determine how currents and voltages change upon connection.
  • A participant reiterates the initial assumption about potential equalization and introduces the concept of a reference point for potential, noting that voltages remain unchanged if only one point is common.
  • This same participant points out that if the circuits are earthed, connecting them alters the voltages and currents unless the connection points are at the same potential with respect to the ground.
  • Another participant mentions that there could be current flow in the connecting wire if the independent circuits possess capacitance that completes the circuit.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of currents and voltages upon connection, with no consensus reached on the exact outcomes or conditions that govern these changes.

Contextual Notes

The discussion includes assumptions about the nature of the circuits, such as whether they are earthed or possess capacitance, which may affect the outcomes but remain unresolved.

TheCanadian
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If you have two independent circuits, and then connect them at two points that are at arbitrary voltages by a single conductor, what happens to the system? A moment after the connection happens, I would assume there to be no current between the circuits since the two circuits would try and establish equal potential at the two points they're connected by, right? But would that actually happen? If you had a current I1 going through one of the circuits for example, and then connected the two circuits together by this one conductor, would I1 change at that instant (unless the two points the conductor is connected to is at equal potential)?
 
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It may definitely change the currents and voltages in both circuits. In what way will depend on the specifics.
 
TheCanadian said:
If you have two independent circuits, and then connect them at two points that are at arbitrary voltages by a single conductor, what happens to the system? A moment after the connection happens, I would assume there to be no current between the circuits since the two circuits would try and establish equal potential at the two points they're connected by, right? But would that actually happen? If you had a current I1 going through one of the circuits for example, and then connected the two circuits together by this one conductor, would I1 change at that instant (unless the two points the conductor is connected to is at equal potential)?
The potential is defined with respect to a given point. If two circuits have only a single point in common that point can be considered as the zero of potential for both of them. All the voltages (potential differences) are the same as before they get connected.
The situation is different if the circuits are earthed. In this case, connecting them changes the voltages and currents, as they got two points in common, unless the points were at the same potential with respect to the ground.
 
What ehild said.

There might be some current flow in the single the connecting wire if the "independent" circuits actually have some capacitance that completes the circuit.
 

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