Is a resistor a dependent source?

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Discussion Overview

The discussion centers around whether a resistor can be classified as a voltage-controlled current source. Participants explore the characteristics of resistors, their passive nature, and how they interact with voltage and current sources.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that a resistor could be considered a voltage-controlled current source under certain conditions, particularly when used with a voltage source.
  • Others argue that a resistor is fundamentally a passive element defined by Ohm's law, translating voltage to current and vice versa, but not acting as a source by itself.
  • A participant mentions that current sources have very high output resistance and suggests modeling a current source with a large resistor, noting the implications of voltage supply requirements.
  • One participant provides an example illustrating how varying the voltage across a resistor can affect the current, emphasizing the relationship between voltage and current in this context.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether a resistor can be classified as a voltage-controlled current source, with multiple competing views presented regarding the nature and role of resistors.

Contextual Notes

The discussion includes assumptions about the conditions under which a resistor might be modeled as a source, as well as the limitations of using large resistors to approximate current sources.

ch3cooh
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Is a resistor a voltage-controlled current source? WHY?
I think it is but I don't know whether I'm correct.
 
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ch3cooh said:
Is a resistor a voltage-controlled current source? WHY?
I think it is but I don't know whether I'm correct.

Hi ethanoic! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

Not many people would bestow that title on a humble resistor. A resistor can be used, in conjunction with a voltage source, to approximate a current source providing the voltage across that resistor is held approximately constant, and this condition is usually met by arranging that at all times source voltage ≫ load voltage.

By itself, a resistor is not a source of anything. :smile:
 
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A resistor is a passive element, nothing more or less. It's I-V relation is Ohm's law. A voltage source across it will give a current. A current source across it will give a voltage. A resistor can translate V to I or I to V, either way.

Claude
 
Current sources have very high ouput resistance. One way to model a current source is to use a very large value resistor. The down side is you may need a very large voltage source as well.

For example suppose you needed a 1mA current source that operated over the range 0-1V.

If you used a 1000V supply and a 1MOhm resistor then the current would range from...

1000/1000,000 = 1000uA
to
(1000-1)/1000,000 = 999uA

which is reasonably constant over the required voltage range!

Even using a 10V source and a 10K Ohm...

10/10,000 = 1000uA
(10-1)/10,000 = 900uA

Call it 950uA +/- 5%

Within limits the current can be changed by varying the source voltage.
 

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