Does this obey passive sign convention? (Circuits)

AI Thread Summary
The discussion centers on the application of passive sign convention in circuits, particularly when dealing with positive current and negative voltage. It raises the question of whether a positive current entering a positive terminal of a negative voltage still adheres to the convention. The analogy of water pressure is used to explain how current can be viewed in terms of energy gain and loss, highlighting the complexity of interpreting voltage and current directions. Additionally, the ambiguity in labeling components as positive or negative is noted, emphasizing the importance of context in circuit analysis. Ultimately, the interpretation of circuit diagrams can vary based on initial assumptions about current direction.
lillybeans
Messages
67
Reaction score
1
24uyqo5.png


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.
 
Physics news on Phys.org
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.
 
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.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Thread 'A bead-mass oscillatory system problem'
I can't figure out how to find the velocity of the particle at 37 degrees. Basically the bead moves with velocity towards right let's call it v1. The particle moves with some velocity v2. In frame of the bead, the particle is performing circular motion. So v of particle wrt bead would be perpendicular to the string. But how would I find the velocity of particle in ground frame? I tried using vectors to figure it out and the angle is coming out to be extremely long. One equation is by work...
Back
Top