Does this obey passive sign convention? (Circuits)

In summary, the passive sign convention is typically followed by having positive current flow into the positive terminal of an element first. However, in certain cases where the voltage is negative, the positive terminal may actually be the negative terminal, requiring the element to be flipped. This still follows the passive sign convention, as positive current is still flowing into the positive terminal of a negative voltage. The labeling of components and wires may appear ambiguous, but the usual convention is to draw arrows on components to indicate voltage and on wires to indicate current. When applying Kirchoff's laws, incorrect guesses of arrow directions may result in negative magnitudes associated with the arrows. Therefore, the interpretation of the diagram depends on the context.
  • #1
lillybeans
68
1
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I thought passive sign convention is obeyed when you have a positive current flowing into the positive terminal of the element first. But how about this case? While it is drawn that way, the positive terminal is actually the NEGATIVE terminal because the voltage is negative, so you have to flip it.

Does this still count as obeying the passive sign convention then? In other words, POSITIVE current flows into POSITIVE terminal of NEGATIVE voltage.

Thanks in advance.
 
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  • #2
Imagine you have a system that pumps water in a cycle. If the water goes up some hill in the process then it gains potential energy, and ,conversely, loses potential energy for when water flows downward. If the current flows from the negative end of the resistor to the positive, it has gained voltage, as if the water moved to a higher potential. Current can be thought of as water pressure in our imaginary system. If the water flows uphill to a higher potential then the water pressure will be less as energy was exerted to push the water, so likewise, current will be negative.
 
  • #3
The labeling appears ambiguous:
Does the + and - sign indicate the cathode and anode of the component, or which end is more positive than the other wrt to the voltage?

If the + end has the higher potential, the the voltage measured from - to + is 11.3mV and the current flows in the direction of the arrow through the component.

The usual convention is to draw arrows on components showing voltage and on wires showing current.

When applying kirkoffs laws we often have to guess the arrow directions at the start. If we guess wrong, then the magnitude that ends up associated with the arrow will be negative.

So the interpretation of the diagram depends on the context.
 

Related to Does this obey passive sign convention? (Circuits)

1. What is the passive sign convention in circuits?

The passive sign convention is a set of rules used to determine the polarity of voltage and current in a circuit. It states that the current flows from higher potential to lower potential and the voltage drop across a resistor is in the same direction as the current flow.

2. How do I apply the passive sign convention in a circuit?

To apply the passive sign convention, assign a direction for the current flow in each branch of the circuit. Then, for each resistor, the voltage drop should be in the same direction as the assigned current flow. If the voltage drop is in the opposite direction, the current flow should be assigned in the opposite direction as well.

3. What happens if the passive sign convention is not followed in a circuit?

If the passive sign convention is not followed, it can lead to incorrect calculations and analysis of the circuit. This can result in incorrect predictions and potential errors in the circuit's functioning.

4. Can the passive sign convention be applied to both DC and AC circuits?

Yes, the passive sign convention can be applied to both DC (direct current) and AC (alternating current) circuits. However, it is important to note that the convention may not always hold true in complex circuits with non-linear components.

5. Why is the passive sign convention important in circuit analysis?

The passive sign convention is important in circuit analysis as it ensures consistency in calculations and helps to determine the correct direction of current flow in a circuit. It also aids in simplifying the analysis process and makes it easier to understand the functioning of the circuit.

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