- #1
How does a resistor exactly reduce current flow in a circuit
- Thread starter tor2006
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Discussion Overview
The discussion revolves around the functioning of resistors in electrical circuits, particularly how they reduce current flow. Participants explore concepts related to electron movement, resistance properties of materials, and the nature of electrical current.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants propose that a resistor acts as a physical obstruction to current flow, but they express uncertainty about the exact mechanisms involved.
- One participant compares current flow to a bicycle chain, suggesting that while current moves, the actual movement of electrons is much slower than commonly perceived.
- It is noted that the number of electrons entering and leaving a battery must be equal, implying a balance in current flow.
- Resistance is described as a property of materials, with metals having more free electrons and thus generally lower resistance. Higher resistance correlates with fewer free electrons, which are responsible for carrying current.
- There is contention regarding the speed of electricity in conductors, with some participants asserting that it does not travel at the speed of light but rather at a lower speed, while others clarify that only the electromagnetic wave travels close to light speed.
- One participant emphasizes that the drift velocity of electrons is significantly slower, ranging from millimeters to centimeters per second, depending on the conductor and current magnitude.
- A question is raised about whether a longitudinal wave of compression and rarefaction travels through the outer electrons in the conductor.
Areas of Agreement / Disagreement
Participants express differing views on the speed of electricity in conductors and the relationship between current and electron movement. The discussion remains unresolved with multiple competing perspectives on these topics.
Contextual Notes
There are limitations in the discussion regarding the assumptions made about the nature of current and electron movement, as well as the definitions of terms like "electricity" and "current." Unresolved mathematical steps and the scope of the discussion are also noted.
- #2
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Current is like a bicycle chain --- all parts move at the same time. Actual electron movement is MUCH slower than you probably imagine. Google "drift current"tor2006 said:
- #3
tech99
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You may also notice that the number of electrons entering and leaving the battery are equal. So one side cannot flow faster than the other.
- #4
Frenemy90210
tor2006 said:
Resistance is a property of the material; e.g. Metals have a lot of free electrons, which means in general they have less resistance. Higher the resistance, lesser the number of free electrons in the material. These electrons are what carries the current. (at speed of light)
- #5
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No, electricity in conductors does not travel at c but at a slightly lower speed.Frenemy90210 said:
https://www.physicsforums.com/threads/electricity-doesnt-move-at-the-speed-of-light.5367/
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davenn
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phinds said:
No, they travel even slower ... Drift velocity is mm to cm / sec depending on conductor and magnitude of the current
https://en.wikipedia.org/wiki/Drift_velocity
The only thing that travels at near the speed of light is the pulse of the EM wave along the outside of the conductor
In a DC circuit, it is a single initial pulse when the circuit is switched on. In an AC circuit, it is a cycling pulse at the rate of the AC signal frequencyDave
- #7
tech99
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A longitudinal wave of compression and rarefaction must also travel through the outer electrons in the conductor. Or not?davenn said:
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I specifically was not talking about electrons and drift velocity but electricity (that is, current)davenn said:
- #9
davenn
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phinds said:
basically the same thing ... current is the flow/movement of charge (s), those charges are the electrons
As I said, Only the EM wave travels at near light speed
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