What Causes Electromagnetic Induction in a Conductor?

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Discussion Overview

The discussion centers on the causes of electromagnetic induction in conductors, exploring the behavior of charges within a magnetic field and the role of forces acting on both positive and negative charges. Participants delve into the mechanics of current generation and the constraints on charge movement in solid conductors.

Discussion Character

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

Main Points Raised

  • One participant questions the mechanism of current setup in a conductor when both positive and negative charges experience Lorentz forces.
  • Another participant explains that positive charges are fixed in the atomic lattice and cannot move, while electrons are free to move.
  • It is noted that in metals, the positive charges (ionic cores) are bound and cannot be displaced by the Lorentz force, allowing only electrons to contribute to current.
  • A participant seeks clarification on the concept of positive charges being bound in the lattice, emphasizing that if they were free, the material would behave like a liquid.
  • Discussion includes the nature of nuclear forces, with one participant stating that while nuclei could theoretically move under Lorentz forces, they are bound to other nuclei, affecting their mobility.
  • Another participant elaborates on the strength of nuclear forces compared to electromagnetic forces, using an analogy to illustrate the relative strength of these forces in holding atomic structures together.
  • Questions arise regarding the specific forces that bind nuclei in solids and the implications of charge movement in response to external forces.

Areas of Agreement / Disagreement

Participants express varying views on the movement of charges in conductors, with some agreeing on the fixed nature of positive charges while others explore the implications of nuclear forces. The discussion remains unresolved regarding the detailed mechanics of charge movement and the binding forces at play.

Contextual Notes

Participants reference concepts such as Lorentz force, nuclear force, and the behavior of charges in different states of matter, indicating a reliance on specific definitions and assumptions that may not be universally agreed upon.

eightsquare
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When a conductor carries current, due to Lorentz force, the conductor experiences a force. However I was wondering what causes electromagnetic induction. Moving a conductor in a magnetic field causes its charges to experience a Lorentz force, but unlike the case of the current, here both the positive and the negative charges are moving, so both of them feel a force. So how is a current set up? Why don't the positive charges move?
 
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The opposite charges will be under the action of forces in opposite directions. The positive charges won't move because they are attached to the fixed nuclei. The electron's are free to move
 
Yes, they both feel Lorentz forces. And if they are "free", they both move.
The motions will be in opposite directions so the currents will add up.

In a metal the positive charges (ionic cores) are bound together in the lattice and the Lorentz force cannot "move" them. The electrons are the only free charge carriers in this case.
 
What do you mean 'in a metal the positive charges are bound together in the lattice'?
 
The positive charges are fixed. The nuclei of the atoms are not free to move around. If they were free to move you would have a liquid, not a solid
 
Conductors only have free electrons because of their electronic configuration.Positive charges in conductors are present inside the nucleus of the atom where they are bound by strong nuclear forces and this nucleus is constrained inside the metal lattice and hence these positive charges cannot move across the conductor .So the positive charges also experience lorentz force but that force is not enough to move the protons or the nucleus.
 
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The nuclear force binds the protons and neutrons together in the nucleus. But this is not so relevant here. The nucleus (positive) could move under the effect of the Lorentz force if it were not bound to the other nuclei in the crystal. They also are more massive than the electrons so even if they were free their motion will be much slower.

In a ionic solution both positive and negative ions (their nuclei included) move under the effect of external fields.
 
Ok thanks. I was wondering how the nuclear force can hold the protons in place. If the protons are subject to force and accelerate they can drag the neutrons along with them. Could you please elaborate on how 'if they were not bound to the other nuclei in the crystal'? Which force binds them exactly?
 
eightsquare said:
Ok thanks. I was wondering how the nuclear force can hold the protons in place. If the protons are subject to force and accelerate they can drag the neutrons along with them.
The nuclear force is very strong compared to the electromagnetic forces from magnetic fields in your lab. It's like picking up an apple: you pick up the whole apple and not just the shell (where you apply the force), as the internal forces (holding the apple together) are very strong compared to the force of you, lifting the apple.

Could you please elaborate on how 'if they were not bound to the other nuclei in the crystal'? Which force binds them exactly?
If you try to move a nucleus in a solid, the electrons surrounding this nucleus will move as well (to stay in their orbits), but then they get repelled by electrons of other atoms nearby.
In addition, there are electrons in chemical bonds, keeping the atoms together and at a fixed distance (again, due to electromagnetic forces), but that needs some quantum mechanics for a proper description.
 
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Okay thanks!
 

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