Coaxial cable with unequal currents

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SUMMARY

The discussion centers on analyzing an unbalanced coaxial cable where the inner current is +100 mA and the outer current is -90 mA. The key equation applied is Ampere's Law, specifically ∫B•dl = μo*Ienc, to determine the enclosed current. The correct enclosed current is +10 mA, derived from the difference between the inner and outer currents. This results in a magnetic field rotating in the phi-direction, with a net current of 10 mA flowing along the z-axis.

PREREQUISITES
  • Understanding of Ampere's Law and its application
  • Familiarity with cylindrical symmetry in current distributions
  • Basic knowledge of magnetic fields and their properties
  • Ability to perform vector calculus operations
NEXT STEPS
  • Study the applications of Ampere's Law in different geometries
  • Explore the effects of unbalanced currents on electromagnetic fields
  • Learn about coaxial cable design and its implications in electrical engineering
  • Investigate the relationship between current distribution and magnetic field strength
USEFUL FOR

Electrical engineering students, physicists, and professionals working with electromagnetic theory and coaxial cable design will benefit from this discussion.

satchmo05
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1. Homework Statement
I just have a question concerning an unbalanced coaxial cable. By unbalanced, I mean that the inner and outer currents are not equal magnitudes of the opposite direction of each other. My homework problem has an inner current of +100[mA] and an outer current of 90[mA] in the opposite direction. My question is regarding the form of the answer.


2. Homework Equations
Cylindrically symmetric current distribution - able to use Ampere's Law here!
Bdl = μo*Ienc

3. The Attempt at a Solution
Implementing the cylindrically symmetric current distribution, the left side of the equation ends up being:
2∏ρ*BФ(ρ) = ...
However, the right side of the equation is where I am having trouble. Would the enclosed current be equal to +10[mA] (100-90[mA]), or something else? An enclosed current of 10[mA] to me makes sense, because if I were an observer looking at the cable, I would only see a magnetic field rotating in the phi-direction, with a current of 10[mA] flowing up the z-axis. I appreciate all help in advance! Thank you much!
 
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You are correct.
 

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