Understanding Magnetic Field Hand Rules

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Discussion Overview

The discussion revolves around understanding how to determine the direction of a compass needle in relation to the magnetic field generated by an electric circuit, specifically focusing on hand rules and the behavior of the magnetic field around a straight wire.

Discussion Character

  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant seeks clarification on how to determine the direction a compass arrow will point when placed above or below an electric circuit.
  • Another participant explains the right-hand rule, indicating that curling the fingers around the wire with the thumb pointing in the direction of the current shows the direction of the magnetic field, which aligns with the compass needle's direction when placed near the wire.
  • A follow-up question is raised about the behavior of the compass needle when it is moved from above the wire to below it, indicating confusion about the changes in direction.
  • A participant responds that the compass needle will adjust to align with the magnetic field, swinging 180 degrees when moved from above to below the wire due to the reversal of the magnetic field direction.

Areas of Agreement / Disagreement

Participants seem to agree on the application of the right-hand rule and the behavior of the compass needle in relation to the magnetic field, but there is still some confusion regarding the specifics of how the compass needle behaves when transitioning between positions above and below the wire.

Contextual Notes

The discussion does not address potential limitations in understanding the magnetic field's behavior in more complex circuits or configurations beyond a straight wire.

Mceestix
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Hey everyone. Just a quick high school physics question about determining magnetic fields using Hand rules.

The only thing I have trouble trying to understand is how to determine the way a compass arrow will point if you place it on top, or under an electric circuit. I know that they are opposites of each other , but i get confused trying to determine them. Any help would be appreciated.. thanks.
 
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You mean a (more or less) straight wire, right? Curl the fingers of your right hand around the wire so that your thumb points in the direction of the current. The magnetic field runs in circles around the wire, in the direction that your fingers are curling. This is also the direction that a compass needle will point if you place it near the wire.
 
jtbell said:
You mean a (more or less) straight wire, right? Curl the fingers of your right hand around the wire so that your thumb points in the direction of the current. The magnetic field runs in circles around the wire, in the direction that your fingers are curling. This is also the direction that a compass needle will point if you place it near the wire.

Oh okay, that does make sense now... but what about the changes that happen to the compass if you place it on top of the wire, versus below the wire?
 
The compass needle will align itself with the field--as you move the compass up, down, and around the wire, the needle will adjust itself to always point in the direction of the field. So if you move the compass from above the wire to below the wire, the needle will swing 180 degrees to point in the other direction, since the magnetic field reverses direction.
 

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