How Does Quantum Mechanics Influence Voltage in Rotating Magnetic Fields?

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Discussion Overview

The discussion centers on the influence of quantum mechanics on voltage in rotating magnetic fields, particularly focusing on the behavior of charge and potential energy in conductive loops. Participants explore concepts related to induced electromotive force (emf), charge density, and the behavior of electrons in conductive materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a scenario involving an open circuited loop rotating in a magnetic field, questioning how potential energy is stored in the loop and whether electrons are elevated to higher energy levels.
  • Another participant notes that charge density can change slightly with a voltage difference but suggests this effect is negligible without a capacitor in the circuit.
  • A participant raises a question about connecting a copper wire to the anode of a battery, proposing that the charge density would spread across the wire until it matches the anode's charge.
  • One participant challenges the idea of significant charge density difference, asking for clarification on the amount of charge associated with a few volts and a free wire.
  • Another participant expresses skepticism about the usefulness of the term "generated" in this context and emphasizes that the tiny charges involved are negligible for practical applications, also noting that a battery operates differently than a capacitor.

Areas of Agreement / Disagreement

Participants express differing views on the significance of charge density differences and the behavior of charge in conductive materials. The discussion remains unresolved, with multiple competing perspectives on these concepts.

Contextual Notes

Participants have not reached consensus on the implications of charge density changes or the comparison between battery operation and capacitors. The discussion includes assumptions about the behavior of electrons and the nature of induced emf that may not be fully explored.

jaydnul
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Say you take an open circuited loop (not connected back to itself) and measure its voltage relative to some external reference point. Then you start rotating this loop in a magnetic field. Depending on the power of your motor, the loop will continue to spin for a finite amount of time. After this, the voltage with respect to the external reference point is much greater than it was before we rotated it.

My question is how this potential energy is stored in the conductive loop. The overall charge of the loop did not change. Were the electrons bumped up to higher energy levels? If so , how does that translate to the movement of charge (current) when the circuit is closed?

Edit: Nvm, I realize where I am going wrong. When the coil is not rotating, there will be no induced emf. Although answering my own question has raised another one; does each nucleus of the conductor (copper for example) have the same number of electrons associated with its outer shell? Or can the density of electrons vary in the conductor?
 
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The charge density can change a tiny bit if you have a voltage difference, but unless you put a capacitor in the circuit this effect is negligible.
 
What about if you connect a copper wire to the anode of a battery?

The anode of the battery has a considerable difference in charge density compared to the neutral wire, with a net negative charge. So if you connect the wire to the anode only, wouldn't that charge density spread across the whole wire (the battery would continue to output charge until the wire reached the same net charge as the anode was originally)?
 
Jd0g33 said:
The anode of the battery has a considerable difference in charge density compared to the neutral wire
Does it? How many femtocoulombs do you get from a few volts difference and a free wire somewhere?
 
mfb said:
Does it? How many femtocoulombs do you get from a few volts difference and a free wire somewhere?

But the entire voltage of the battery is generated from this small difference in charge density, is it not?
 
I don't think "generated" is a useful concept here. It corresponds to. And those tiny charges are negligible for practical applications.
And a battery does not work like a capacitor.
 

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