Current Carrying Wires: How Ampere's Law Affects Safety

Click For Summary

Discussion Overview

The discussion revolves around the safety of current-carrying wires in circuits, specifically addressing why wires do not touch each other and cause short circuits. It explores the implications of Ampere's Law in practical scenarios, including the forces between wires and the role of insulation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why wires in circuits do not touch each other and suggests that attractive forces from Ampere's Law could cause them to do so if they carry current in the same direction.
  • Another participant argues that the forces between two wires carrying typical currents are negligible, which is why practical applications like electromagnets require multiple wire turns and an iron core.
  • It is noted that wires are usually insulated to prevent short circuits, making bare conductors rare in typical applications.
  • A participant acknowledges that while attractive forces exist in principle, they are minimal in normal circuit conditions, but highlights exceptions in high-current scenarios such as short circuits, large power generators, and specific applications like particle accelerators and rail guns.
  • A personal anecdote is shared about a development project involving three-phase power, where the wires became closely aligned under high current conditions, illustrating the potential dangers of high currents.

Areas of Agreement / Disagreement

Participants express varying views on the significance of the forces between current-carrying wires, with some emphasizing the negligible nature of these forces in typical circuits while others point out exceptions in high-current situations. The discussion does not reach a consensus on the implications of Ampere's Law in practical applications.

Contextual Notes

The discussion highlights limitations in understanding the forces involved, particularly in different current scenarios, and the dependence on specific conditions such as insulation and wire configuration.

palkia
Messages
52
Reaction score
2
Why don't wires in any circuit touch each other and get short circuited?

If two current carrying wires carry charges in same direction then from ampere's law,can't they touch each other due to attractive forces?
 
Physics news on Phys.org
The force between two wires is actually not much for practical values of current. This is why strong electromagnets need to use many turns of wire and an Iron core. two wires in a typical circuit will not even twitch. (You can do the sums if you look up Ampere's Law - see this wiki link.)
 
Wires are often covered in an insulating coating/cover that prevents short circuits as well. It's extremely rare to find long strands of bare conductor except perhaps in mains power lines.
 
  • Like
Likes   Reactions: sophiecentaur
palkia said:
If two current carrying wires carry charges in same direction then from ampere's law,can't they touch each other due to attractive forces?

That's true in principle, but in actual practice with "normal" values of current such as on a circuit board, the forces are negligible.

However there are exceptions and very abnormal cases.
  • Short circuits in power systems cause enormous currents.
  • Large power generators need powerful restraints to keep them from flying apart.
  • Magnets in particle accelerators experience large forces.
  • The Navy's "rail gun" would fly apart if not confined.
 
Many years ago I was working on a large piece of equipment that was fed with 3-phase power with a drop from the ceiling. Since this was a development project, the incoming power was just three wires hanging down without a conduit. When the many-kilowatt heater switched on those three conductors became Siamese Triplets. I'm sure any finger in the way would have been removed from the previous owners hand!
 
  • Like
Likes   Reactions: Drakkith

Similar threads

  • · Replies 9 ·
Replies
9
Views
1K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 27 ·
Replies
27
Views
3K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 61 ·
3
Replies
61
Views
6K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K