How to model internal resistance

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Discussion Overview

The discussion revolves around modeling internal resistance in electrical circuits, particularly in the context of measuring voltage generated by a coil with a magnet passing through it. Participants explore the appropriate representation of a battery or voltage source in circuit diagrams and the implications of internal resistance on voltage measurements.

Discussion Character

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

Main Points Raised

  • One participant questions whether a coil with thin wire and a magnet can accurately measure total voltage when connected to a voltmeter.
  • Another participant challenges the idea of modeling a battery as an inductor and seeks clarification on the original question.
  • A participant suggests that the standard model for a DC battery is an ideal voltage generator in parallel with a resistor, contrasting it with AC voltage sources.
  • A beginner participant expresses uncertainty about terminology and confirms the assumption of a DC source, discussing how to calculate EMF using equations related to the coil's properties.
  • The same participant questions whether a voltmeter would reveal a 50 V difference given a known internal resistance of 20 ohms in the circuit.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the modeling of the circuit or the implications of internal resistance on voltage measurements. Multiple competing views and uncertainties remain regarding the appropriate representation of voltage sources and the effects of internal resistance.

Contextual Notes

Participants express varying levels of understanding of circuit terminology and concepts, indicating potential limitations in their assumptions and definitions. The discussion also highlights the need for clarity in distinguishing between AC and DC sources.

Who May Find This Useful

Individuals interested in electrical engineering, circuit design, and the principles of electromagnetism may find this discussion relevant.

Cspeed
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If I set up a coil with thin wire, push a magnet through it, and connect either end to a voltmeter (in series), then is this an accurate way to measure the total voltage? I might not be phrasing this right, so ask me to clarify if I should. I'm guessing that you can't just simplify a circuit like this by drawing a battery as the inductor and just add a resistor to the side which stands for the internal resistance. Or can you?
 
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Why would you model a battery as an inductor? And I don't know what you're trying to ask.
 
I'm guessing that you can't just simplify a circuit like this by drawing a battery as the inductor and just add a resistor to the side which stands for the internal resistance.

Are you trying to model an ac or a dc source?
The usual model for a dc battery is an ideal voltage generator in parallel with a resistor...if you are trying to model an ac voltage source, typically a rotating piece of machinery such as an alternator, I'm sure there are standard models available...
 
I might not be using the terms correctly, as I'm only a beginner with circuitry. I used the term inductor to describe a source of voltage. I'll assume that it's DC (a coil of wires that have magnetic flux go from A to B).

Using equations for the area of the loops, the number of turns, and the magnetic field, I can get the EMF. Now, let's assume that using equations gives me an EMF of 50 V. If those coils of wire have an internal resistance known to be 20 ohms, then will connecting a voltmeter to the circuit reveal a 50 V difference between either end of the voltage source?
 

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