Understanding Voltage Distribution in Series Circuits

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Discussion Overview

The discussion revolves around the concept of voltage distribution in series circuits, focusing on how voltage drops across resistors relate to their resistance and the role of the electric field in this process. Participants explore theoretical aspects, analogies, and the implications of Ohm's Law.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that the electric field is responsible for setting the voltage drops across resistors, with higher resistance leading to larger voltage drops due to the constant current in the circuit.
  • Others emphasize the importance of Ohm's Law (V=IR) in explaining why voltage drops are larger across higher resistors, given that the current remains the same.
  • A participant introduces an analogy of a scree slope to illustrate how energy is lost across different resistors, suggesting that the arrangement of resistors and the battery determines the "slope" of energy loss.
  • There is a discussion about the terminology used to describe the electric field, with one participant suggesting that "flows" is not an appropriate term, and instead proposing that the change in the field propagates when the circuit is completed.
  • Another participant notes that the arrangement of fields in a circuit can vary significantly based on the layout and components used, questioning the relevance of considering the electric field in circuit analysis compared to potential difference.

Areas of Agreement / Disagreement

Participants generally agree on the application of Ohm's Law to explain voltage drops in series circuits, but there are differing views on the role and terminology of the electric field, as well as the relevance of field arrangements in circuit analysis. The discussion remains unresolved regarding the best way to conceptualize these ideas.

Contextual Notes

Some limitations include the dependence on definitions of electric field and potential, as well as the varying interpretations of how energy is distributed in the circuit. The discussion does not resolve the complexities of these concepts.

Glenn G
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Say you have two separate resistors in a circuit. When you close the switch on the circuit is it the electric field that flows through the circuit that effectively sets the voltage drops so a bigger voltage drop occurs across the higher resistor in proportion to its resistance such that the current flow in the circuit is constant.
I'm aware of W=Q V and so as a coulomb then flow through the larger resistance more energy is transferred there than in the smaller resistance.
 
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It is the electric field that sets the voltage drops (without electric field we can't have voltage anywhere, though if you study more advanced electromagnetism, it is the scalar potential V that is more fundamental than the electric field) but you forgot to mention Ohm's Law V=IR which is the basic reason that the voltage drop is bigger in the higher resistor (since current is the same, with higher resistance R there must be higher voltage V due to V=IR).
 
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Would a useful analogy to maybe think of a scree slope which is already mapped out with a guy at the top with a certain amount of gpe and that there is one steep drop that represents the larger voltage drop and then a shallower drop later on that represents the smaller voltage drop across the smaller resistance... of course you've got to get the guy back to the top of the scree slope to start over again (like energy input from a batter in the form of a winch say) so the guy has no choice as to where he loses his energy it is pre-determined if you like

get a different set of resistors and a different battery and you get a new pre-determined scree slope set up.
 
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Glenn G said:
When you close the switch on the circuit is it the electric field that flows through the circuit that effectively sets the voltage drops so a bigger voltage drop occurs across the higher resistor in proportion to its resistance such that the current flow in the circuit is constant.

Here is one way to think about it...

The voltage and the combined resistance dictate the current that flows around the circuit...

I = V/R or in this case...
I=V/(R1+R2)

Then current and the individual resistance dictates the individual voltages across the resistors..

VR1 = I * R1
VR2 = I * R2

and

V = VR1 + VR2
 
Glenn G said:
voltage drops so a bigger voltage drop occurs across the higher resistor in proportion to its resistance such that the current flow in the circuit is constant.

only if the initial voltage is higher, see delta's comment

Delta² said:
but you forgot to mention Ohm's Law V=IR which is the basic reason that the voltage drop is bigger in the higher resistor (since current is the same, with higher resistance R there must be higher voltage V due to V=IR).

exactly !
 
Glenn G said:
is it the electric field that flows through the circuit
"flows" is not a good term to use here. You could say that the change in field Propagates, from the instant the circuit is completed and a new steady state is reached. All the basic theory on resistive circuits deals with that steady state situation.
However, the arrangement of (macroscopic) fields is not very relevant. The Field (Volts per metre) will vary a lot depending how you lay the circuit wires out and choose different sized components so it's not a lot of use to consider that. The layout of the charges flowing around the circuit will depend on the local field effects - interactions between neighbouring charges. The reason that Potential is used more, in circuit analysis is that it is more suitable. There is no fundamental hierarchy which makes Field or Potential more important so it's not necessary that a Force makes a change, any more than a Potential Difference.
 
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