Self induction in a straight wire

  • Context: Graduate 
  • Thread starter Thread starter jpo
  • Start date Start date
  • Tags Tags
    Induction Self Wire
Click For Summary

Discussion Overview

The discussion centers around the concept of self-induction in a straight wire, particularly in the context of a decreasing direct current (I) and the implications of Lenz's law. Participants explore the nature of inductance, the generation of magnetic fields, and the source of energy in self-induction scenarios.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a decreasing current will produce a self-induced current in the same direction as I, referencing Lenz's law.
  • Another participant suggests that the system must react against the change, implying a resistance to the change in current.
  • A different viewpoint proposes that inductivity arises from the resistance to changes in current, requiring a significant magnetic field to facilitate current flow through the wire.
  • One participant raises a concern about the existence of inductance in a straight wire, noting the absence of a loop and magnetic flux.
  • In response, another participant asserts that a straight wire can indeed exhibit inductance without needing a loop.
  • It is mentioned that any change in current through any conductor will generate a magnetic field, with the relationship to inductance being governed by Lenz's law.
  • One participant expresses curiosity about the source of energy for self-induction when the current decreases, questioning where the additional current would come from.
  • A later reply suggests that the magnetic field itself stores energy, which was accumulated as the current increased.

Areas of Agreement / Disagreement

Participants express differing views on the nature of self-induction in a straight wire, particularly regarding the necessity of a loop and the implications of Lenz's law. The discussion remains unresolved with multiple competing perspectives on the topic.

Contextual Notes

Some participants highlight the need for further clarification on the assumptions regarding inductance in straight wires and the conditions under which self-induction occurs.

jpo
Messages
46
Reaction score
0
Direct current I in a straight wire is decreasing with time. Let's assume dI/dt is large. Will such change produce self-induced current in the direction of I?


If Lenz's law is an equivalent of Newton's 3rd law, how come changes in straight wire meet no resistance?
 
Physics news on Phys.org
It seems to me that the system has to react against the change. Is this true?
 
i think that is where inductivity comes from or the resistance of change of current. and you need a large field to push the current throw the wire.
 
My question is will there be such inductance. I mean, there is no loop and no flux through it
 
yes. you don't need a loop. a strait wire will do the trick.
 
any change in current through any object, whether it be a coil or a straight wire, will produce a magnetic field (inductance). The relationship of inductance to the change in current is calculated by lenz's law
 
Current decreases with time. Self induction has to presumably supply extra Amps to resist the change. Where will the energy com from to do all this?
 
jpo said:
Current decreases with time. Self induction has to presumably supply extra Amps to resist the change. Where will the energy com from to do all this?

The magnetic field stores energy. This energy was put there as the current ramped up.
 
mrspeedybob,
this seems very reasonable, thank you!
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 14 ·
Replies
14
Views
4K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 16 ·
Replies
16
Views
5K
  • · Replies 15 ·
Replies
15
Views
6K