Circuit analysis -- Voltage question

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Discussion Overview

The discussion revolves around the representation of output voltages in circuit diagrams, specifically addressing how to interpret V out and the implications of circuit connections on voltage and current flow. The scope includes conceptual understanding and technical clarification related to circuit analysis.

Discussion Character

  • Conceptual clarification, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether V out always represents the voltage between two horizontal lines in circuit diagrams and expresses uncertainty about current flow into those lines.
  • Another participant asserts that if the output nodes are not connected to anything, no current flows to those nodes, and explains that V out in an open circuit condition is equal to the forward voltage drop of a diode.
  • A participant inquires about the reasoning behind the assertion that connecting a wire between terminals implies V out would be zero.
  • Another participant responds that a true short circuit has no potential difference across it, leading to zero voltage, regardless of the current passing through.

Areas of Agreement / Disagreement

There is some agreement on the interpretation of V out in open circuit conditions, but the reasoning behind the implications of short circuits and their effect on V out remains contested.

Contextual Notes

The discussion includes assumptions about circuit conditions, such as whether nodes are connected or open, which affect the interpretation of voltage and current. The implications of short circuits on voltage are also discussed without resolution.

Jamessamuel
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hello,

i have a question regarding the way we represent information on circuit diagrams.

The first is to do with representing output voltages:
12243789_1651989198375566_1915806819_n.jpg


is V out always simply representing the voltage of whatever lies between/trapped between those two horizontal lines? Also, i see a lot of diagrams like this and am asked to determine v out. However, I am not sure whether or not current would flow into those horizontal lines protruding out to those 2 nodes. I don't know what's been connected in there... do i need to know? does current "split" at that top junction?

regards

james.
 
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Jamessamuel said:
is V out always simply representing the voltage of whatever lies between/trapped between those two horizontal lines?

In short yes.

Also, i see a lot of diagrams like this and am asked to determine v out. However, I am not sure whether or not current would flow into those horizontal lines protruding out to those 2 nodes. I don't know what's been connected in there... do i need to know? does current "split" at that top junction?

If the output nodes are NOT connected to anything then no current flows "out to those nodes". In the drawing you posted the output is open circuit (nothing connected to the output) so the current does not split at that top junction. It all goes through the diode. Vout would be known as the "open circuit output voltage". In your example the open circuit output voltage would be equal to the forward voltage drop of the diode. Typically about 0.7V for small silicon diodes.

In other circuits there might be something connected to the output and then that has to be taken into account. For example if the output terminals were connected together with a wire we would say the output has been "short circuited". The output voltage would be zero but there might be current flowing in the wire. This would be known as the "short circuit output current". In your example the short circuit output current would be 5/2500= 2mA
 
thank you for clarifying- i do have one other question though,

when you say there could be a wire between the terminals, why does that imply the V out would be zero?
 
Jamessamuel said:
why does that imply the V out would be zero?
A true short circuit has no PD across it, whatever current is passing through it. R=0 so IR = 0
 

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