Conceptual Question about Voltage Drops

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Homework Help Overview

The discussion revolves around understanding current in series circuits, particularly how current is determined before encountering resistors. The original poster presents a scenario involving a simple DC circuit with a battery and resistors, expressing confusion about how electrons "know" their speed in relation to resistances ahead.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore analogies to clarify the behavior of current, such as comparing it to a bicycle chain and discussing the influence of electric fields in the circuit. Questions about the nature of electron movement and the initial transient response in circuits are raised.

Discussion Status

The discussion is ongoing, with participants providing analogies and suggesting resources for further understanding. There is an exploration of different interpretations regarding how current behaves in relation to circuit components, but no consensus has been reached yet.

Contextual Notes

Some participants mention the transient response in circuits and the influence of electric fields, indicating that there may be underlying concepts that require further exploration. The original poster expresses a willingness to clarify their explanation if needed.

Jason Williams
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So I have one last roadblock to understanding how circuits fully work and it has to do with currents (in series). To my current understanding, if we were to have a simple DC circuit with one battery at 10V and one resistor at 10 ohms, the current at all points in the wire is 1 A. Now, if we were to connect another resistor of 10 ohms, the current would be then be .5 A.

I am essentially trying to figure out how is the current determined in the wire before it encounters any resistors. What I don't understand here is how is it possible for the electrons to know what speed to travel with when it doesn't know the resistances that are ahead of it? Shouldn't as much charge as possible be trying to escape the terminal of the battery regardless of the resistors ahead?

If the way I'm explaining it doesn't make any sense, I will gladly offer up a different explanation.

Thanks!
 
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I always find it helpful to think of current as being like a bicycle chain. It doesn't make any sense to try to think of one link in the chain moving by itself. Either all links move at the same time or no links move.
 
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Jason Williams said:
So I have one last roadblock to understanding how circuits fully work and it has to do with currents (in series). To my current understanding, if we were to have a simple DC circuit with one battery at 10V and one resistor at 10 ohms, the current at all points in the wire is 1 A. Now, if we were to connect another resistor of 10 ohms, the current would be then be .5 A.

I am essentially trying to figure out how is the current determined in the wire before it encounters any resistors. What I don't understand here is how is it possible for the electrons to know what speed to travel with when it doesn't know the resistances that are ahead of it? Shouldn't as much charge as possible be trying to escape the terminal of the battery regardless of the resistors ahead?

If the way I'm explaining it doesn't make any sense, I will gladly offer up a different explanation.

Thanks!
Watch "surface charges and circuits" on youtube.. Answer to your doubt lies in the surface charge feedback theory...You need to understand the very initial transient (which lasts for a few picoseconds) which is hardly discussed in the circuits course..
 
Last edited:
The electrons move inder the influence of the electric field which propagates
through the whole of the circuit. The field is setup by the power supply and
its propagation is influenced by the components in the circuit. I tend to think
of the situation like the ocean (electrons) and islands (the components), except
that the current goes through the islands under the influence of the pressure
difference (as evident by the waves present there) created on the shores of the islands.
 

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