Resistors in series - how can current be constant?

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Discussion Overview

The discussion centers around the behavior of current in series circuits, particularly how the current remains constant despite the addition of resistors. Participants explore the implications of resistance on current flow and seek clarification on the underlying principles.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions how current can remain unchanged in a series circuit with multiple resistors, suggesting an analogy involving cars on a roundabout to illustrate their confusion.
  • Another participant references a video that states the current through each resistor in series is the same, leading to a realization about the relationship between overall current and individual readings.
  • Some participants assert that while the overall current decreases with added resistance, the current through each resistor remains equal to the overall current.
  • There is a discussion about the implications of unequal current, with one participant noting that if current were not the same everywhere, it would lead to electron buildup and the creation of electrostatic fields to equalize the flow.
  • Clarifications are made regarding how adding resistors affects the total current, with one participant suggesting that if the total resistance doubles, the current would halve.

Areas of Agreement / Disagreement

Participants generally agree that the current through each resistor in series is the same, but there is ongoing discussion about how adding resistors affects the overall current. The relationship between resistance and current remains a point of exploration and clarification.

Contextual Notes

Participants express confusion regarding the definitions and analogies used to explain current flow, indicating potential limitations in understanding the concepts of resistance and current in series circuits.

Who May Find This Useful

This discussion may be useful for individuals seeking to understand the principles of current flow in series circuits, particularly those who are new to electrical concepts or are struggling with circuit analysis.

JoeN
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I can't get my head around this:

How can the current in a series circuit be unchanged by any amount of resistors?
1) I understand that there is only one path, and thus;
2) I understand that the charge isn't used up.

BUT. If current is the charge passing a point per second, and resistors are something that 'resist' the charge or slow it down, how can the central question be explained?

Let me explain my reasoning. Take a roundabout and 10 cars, one at the start line and the rest behind each other. Let's say that, when they begin moving, (no acceleration, just constant speed) 5 get to the half way line per second. If I throw in a speed bump a quarter of the way round, this will decrease the cars' speed, and so less cars will pass the half way line per second. The current is decreased?

I've gotten myself thoroughly confused; can anyone explain this simply? Are my definitions wrong, or my analogy, or something?
 
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JoeN said:
I can't get my head around this:

How can the current in a series circuit be unchanged by any amount of resistors?
Why do you think that adding resistors in series doesn't change the current (for a given voltage source)?
 
http://www.youtube.com/watch?v=u-7k8wpl_ZU&list=PLBCCF1129FCAE29DF&index=12&feature=plpp_video

There are three resistors in a series circuit. The video states that the current through the resistors is the same, or 'I = I1 = I2 = I3'.

EDIT: Ah, I see what you mean... so, the overall current is reduced, but the individual current readings through the resistors are equal to each other and the overall current?.. Sorry, I'm just writing my realisations..

If a current is 2A without any resistors, adding two will decrease the current, to say 1A, and this will be the current through the resistor. Is that correct?
 
Last edited:
JoeN said:
If I throw in a speed bump a quarter of the way round, this will decrease the cars' speed,

The spacing between the cars also decreases.
 
JoeN said:
There are three resistors in a series circuit. The video states that the current through the resistors is the same, or 'I = I1 = I2 = I3'.
Sure, the current is the same throughout. (But adding additional resistance in series changes that current.)

If the current were not the same everywhere, that would mean somewhere electrons are building up. If they were to do so, electrostatic fields would quickly be created to stem that flow so that it is evened out.
 
Doc Al said:
Sure, the current is the same throughout. (But adding additional resistance in series changes that current.)

If the current were not the same everywhere, that would mean somewhere electrons are building up. If they were to do so, electrostatic fields would quickly be created to stem that flow so that it is evened out.

The overall current is reduced, but the individual current readings through the resistors are equal to each other and the overall current?..

If a current is 2A without any resistors, adding two will decrease the current, to say 1A, and this will be the current through the resistor. Is that correct?

jtbell said:
The spacing between the cars also decreases.

Ah! Didn't think of that. Thank you, sir.
 
JoeN said:
The overall current is reduced, but the individual current readings through the resistors are equal to each other and the overall current?..
Right.
If a current is 2A without any resistors, adding two will decrease the current, to say 1A, and this will be the current through the resistor. Is that correct?
I'd phrase it like this: If a current is 2A and you add resistors in series to double the total resistance, then the current will drop to 1A and that will be the current through the resistors.
 
Doc Al said:
Right.

I'd phrase it like this: If a current is 2A and you add resistors in series to double the total resistance, then the current will drop to 1A and that will be the current through the resistors.

I see. Thank you very much for your time. Circuits have been troubling me for quite a while.
 

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