Forces between two straight conductors

  • Context: Undergrad 
  • Thread starter Thread starter LogarithmLuke
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Discussion Overview

The discussion revolves around understanding the forces between two straight conductors carrying electric currents. Participants explore the underlying principles, including magnetic fields and the Lorentz force, while seeking clarity on the direction of these forces based on the orientation of the currents.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that currents flowing in the same direction result in attractive forces, while opposite currents lead to repulsive forces.
  • Another participant suggests breaking down the problem into two parts: the magnetic field generated by a current-carrying wire and the Lorentz force acting on a current in a wire.
  • A participant expresses familiarity with the magnetic fields around the wires but struggles with determining the direction of the forces between the conductors.
  • One participant proposes establishing the magnetic field from one wire first, allowing them to analyze the Lorentz force on the second wire without considering the first wire further.
  • A request is made for sketches of the field patterns for both configurations of currents (same and opposite directions) to visualize the attractive and repulsive interactions.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the forces between conductors, with some agreeing on the basic principles while others seek clarification on specific aspects, indicating that the discussion remains unresolved.

Contextual Notes

Participants have not reached a consensus on the best method to determine the direction of forces, and there are unresolved assumptions regarding the application of the right-hand rule and the visual representation of magnetic fields.

LogarithmLuke
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Hi, I am having trouble figuring out how the forces work between two straight conductors with currents going through them. I know that when the currents go the same way, the forces are attractive, and when the currents go opposite ways, the forces are repelling. I know one has to use the right hand rule, but i just can't figure out how to do it to get it right.

Could someone help clear this up?
 
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BvU said:
Hi LL,

Let me give it a try. I find this easiest if split up in two parts:
  1. Magnetic field of a current carrying wire (Ampere's law, Biot-Savart)
  2. Lorentz force on current in a wire (the other one...)

Im aware of what the magnetic fields around the wires look like, the trouble comes with finding the direction of the forces between to conductors.
 
LogarithmLuke said:
Im aware of what the magnetic fields around the wires look like, the trouble comes with finding the direction of the forces between to conductors.
That's exactly what I'm avoiding by first establishing a B field from wire 1 -- after which I can forget wire 1. Wire 2 then experiences a Lorentz force in that B field.
Hyperphysics in fact does it the same way (1 = left, 2= right wire)
 
can you sketch the field patterns for each wire. Can you sketch the resultant field pattern for 2 wires when the currents are in the same direction and in opposite directions. In the same direction the combined field is (visually) attractive.
In opposite directions the combined field is (visually) repulsive.
 

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