Internal resistance proportional to current?

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Discussion Overview

The discussion revolves around the relationship between terminal voltage, internal resistance, and current in a cell with emf. Participants explore the implications of internal resistance on voltage drop and the behavior of terminal potential difference (pd) as current varies. The scope includes conceptual understanding and technical reasoning related to electrical circuits.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions why terminal pd decreases as current increases, linking it to internal resistance and suggesting that internal resistance may increase with current.
  • Another participant asserts that the voltage drop across internal resistance is proportional to the current, indicating that internal resistance is typically assumed to be constant, though this may oversimplify the behavior of some components.
  • There is a repeated inquiry about the extent of voltage lost to internal resistance, with one participant expressing concern over the amount of voltage drop attributed to internal resistance.
  • A participant provides a specific example, stating that if internal resistance is 1 Ohm, then each Amp of current results in a 1 Volt drop, emphasizing the direct relationship between current and voltage drop across internal resistance.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether internal resistance increases with current, and there are differing views on the implications of internal resistance on terminal voltage. The discussion remains unresolved regarding the nature of internal resistance and its effects.

Contextual Notes

Some assumptions about the constancy of internal resistance and the conditions under which it may vary are not fully explored. The discussion also does not clarify the specific definitions of terminal pd and its relationship to other voltage measurements.

CAH
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The terminal voltage and current are measured as the resistance is decresed through a cell with emf and internal resistance. Graph of V (y axis) I (x axis) shows straight line decreasing gradient.
1. Explain why terminal pd decreases as the current increases.

is terminal pd the same as pd/voltage? I thought the pd across a resistor would always be the same provided your not adding resistors. However the mark scheme says:

mention of pd across internal resistance or loss in internal resistance or emf>V,
pd across internal resistance/loss volts increases with current or correct use of equation to demonstrate

So does the internal resistance increase with the current and so voltage is lost through wires?

Thanks :smile:
 
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No. As with all resistances, the voltage dropped across it is proportional to the current and the internal resistance is usually assumed to be constant. That is a bit of an oversimplification for many components, though.
 
so the voltage will continuously drop to internal resistance? It seems like a lot of volts lost just to internal resistance?
 
CAH said:
so the voltage will continuously drop to internal resistance? It seems like a lot of volts lost just to internal resistance?
IF the internal resistance is 1 Ohm then every Amp will cause a drop of 1 Volt. There's no surprise there.
 

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