Electrical components connected between cells

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Discussion Overview

The discussion revolves around circuit theory, specifically the behavior of a circuit with two identical 10V cells and bulbs connected in various configurations. Participants explore how the addition of a bulb affects current and potential difference (pd) in the circuit, considering both series and parallel arrangements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant describes a circuit with two 10V cells and a 1Ω bulb in series, initially calculating a current of 20A and a pd of 20V across the bulb.
  • Another participant suggests that if the bulbs are in parallel, each would experience 20V and draw 20A, assuming ideal batteries.
  • A later reply questions the initial assumption about the configuration, noting that the two cells may no longer be identical and that the number of bulbs has increased.
  • One participant proposes that if the bulb is connected in series with the cells, the total resistance would be 2Ω, leading to a current of 10A with each bulb having a 10V drop across it.
  • Another participant emphasizes the necessity of using Kirchhoff's Laws for circuits with multiple components to determine the behavior accurately.
  • A later reply indicates that the participant has reconsidered their understanding and suggests using Kirchhoff's Laws to analyze the circuit as two series circuits combined.

Areas of Agreement / Disagreement

Participants express differing views on the configuration of the bulbs and cells, leading to multiple interpretations of how to analyze the circuit. There is no consensus on the correct approach or final values for current and pd.

Contextual Notes

Participants highlight the complexity introduced by adding components to the circuit, noting the importance of mathematical tools like Kirchhoff's Laws for accurate analysis. Some assumptions about ideal components and configurations remain unverified.

sorax123
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Hi all,
I would appreciate a little guidance on some circuit theory. I was wondering how a circuit behaves when there are, say two identical 10V cells, and a 1Ω bulb happily sitting in series, but then one connects another identical bulb between the two cells. Obviously the current in the first circuit would be 20A, with the pd across the bulb being 20V. But how would the current and pd values change when the second bulb is connected? I have pondered this for a while, but am unsure what to consider in parallel and hence the currents and pd of each bulb. Would be great for someone to give me a little insight.
Thanks
 
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Hi sorax123. A sketch of what you have in mind would have left readers in no doubt about what you are pondering. It sounds as though the pair of identical bulbs are in parallel? If so, then each sees the 20V across its terminals, so each draws 20A. The batteries, I am assuming, can be considered ideal.)

EDITED
 
Last edited:
http://img836.imageshack.us/img836/3228/19k.png

This should give an idea.
Thanks
 
Last edited by a moderator:
sorax123 said:
This should give an idea.
Thanks

Umm, the two identical cells are no longer identical? And the two bulbs have now become three? :eek:
 
sorax123 said:
Hi all,
I would appreciate a little guidance on some circuit theory. I was wondering how a circuit behaves when there are, say two identical 10V cells, and a 1Ω bulb happily sitting in series, but then one connects another identical bulb between the two cells. Obviously the current in the first circuit would be 20A, with the pd across the bulb being 20V. But how would the current and pd values change when the second bulb is connected? I have pondered this for a while, but am unsure what to consider in parallel and hence the currents and pd of each bulb. Would be great for someone to give me a little insight.
Thanks

Between the cells? So the bulb is connected in series with the cells? If so, then the entire circuit is a series circuit. The resistance in the circuit is 2 ohms, applied voltage is 20 volts, so the current is 10 amps. Each bulb has 10 volts of voltage drop across it, adding up to the required 20 volts of applied voltage.
 
As soon as you get more than tho or three components in a circuit, you really have to use tools like Kirchoff's Laws to find what is going to happen. Just chatting about the problem is unlikely to get anywhere - it's a bit like dealing with money - the Maths will give you an answer. 'Understanding' will only come from familiarity with the Maths and the results it produces.
 
Thanks for replies. The cells in the picture were meant to be 10V each, but having done some more thinking and problems today i think I've gotten to the bottom of it. Using Kirchoff's laws one can treat it as 2 series circuits and then "sum" them in a sense. I think this would be the easiest way to tackle it. Thanks
 

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