Magnetic force between two wires

Click For Summary

Discussion Overview

The discussion revolves around the calculation of the magnetic force between two wires carrying current. Participants explore the implications of high current values, the behavior of superconducting wires, and the validity of the calculations presented.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents calculations for the magnetic force between two wires, including resistance, current, magnetic field strength, and resulting force, questioning the validity of the large force calculated.
  • Another participant confirms the use of V=IR for calculating current but raises concerns about the practicality of such high current values and their implications for wire integrity.
  • A later reply questions whether a superconducting wire would behave differently under the same voltage conditions, suggesting that Ohm's law may not apply in that case.
  • Another participant points out that applying voltage across a superconducting wire could lead to issues with the voltage source due to its internal resistance.

Areas of Agreement / Disagreement

Participants generally agree on the validity of the V=IR relationship but disagree on the implications of using it in the context of superconducting materials and the practicality of the calculated current and force values.

Contextual Notes

There are unresolved assumptions regarding the behavior of superconducting wires under high voltage and the limitations of applying Ohm's law in such scenarios. The calculations presented rely on specific resistance values that may not hold under extreme conditions.

Danyon
Messages
83
Reaction score
1
I'm wanting to know the force between two wires carrying current but I think I did something wrong when I calculated it. Here is my working.
I got a value of 0.0021365 ohms for both wires from http://chemandy.com/calculators/round-wire-resistance-calculator.htm
1000 volts pass through the wires. V=IR so I=V/R which is 1000/0.0021365 = 468055.2305 amps. Is this right?
Magnetic field strength at distance r, where r = 0.01 is B=μ0I/2πr, which is 4π*10^-7*468055.2305/2π*0.01
which equals 9.3611046 tesla. is this right?
Force between the wires is F=BIL where B is 9.3611046 tesla, I is 468055.2305 amps and L equals the length of wire = 0.01 this equals 43815.13971 Newtons. Is this correct? I've checked a few times on my calculator but I still don't believe how large the force is.
 
Physics news on Phys.org
I haven't checked your calculations, but the V=IR one is right.

You might want to consider just how much energy is involved in delivering 400,000+ amps at 1000 V... How does it compare with the output of a commercial power plant? You should expect to see some big numbers, although in practice your wires would vaporize the moment you turned the power on.
 
Nugatory said:
I haven't checked your calculations, but the V=IR one is right.

You might want to consider just how much energy is involved in delivering 400,000+ amps at 1000 V... How does it compare with the output of a commercial power plant? You should expect to see some big numbers, although in practice your wires would vaporize the moment you turned the power on.

Would the wire vaporise at 1000 volts if it where a superconducting wire?
 
If the wire is superconducting then it is not Ohmic and you can't use V = IR.

In reality, if you were to apply that voltage across a superconducting wire, you'd probably melt the voltage source as that still contributes its own internal resistance to the circuit.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 6 ·
Replies
6
Views
988
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 20 ·
Replies
20
Views
5K
  • · Replies 2 ·
Replies
2
Views
9K
  • · Replies 15 ·
Replies
15
Views
4K