The magnetic field outside a coaxial cable

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SUMMARY

The discussion centers on calculating the magnetic field outside a coaxial cable using two different approaches: Ampère's Law and the Biot-Savart Law. Ampère's Law indicates that the magnetic field outside the cable is zero due to the cancellation of currents within the Amperian loop. In contrast, the Biot-Savart Law allows for the calculation of the magnetic field at a specific point by considering the contributions from each current separately, leading to a non-zero value at point B. The participants emphasize the importance of correctly setting up the integral when applying the Biot-Savart Law.

PREREQUISITES
  • Understanding of Ampère's Law
  • Familiarity with the Biot-Savart Law
  • Knowledge of magnetic fields and current distributions
  • Basic calculus for integral setup and evaluation
NEXT STEPS
  • Study the application of Ampère's Law in different geometries
  • Learn how to correctly set up integrals for the Biot-Savart Law
  • Explore the principle of superposition in electromagnetic fields
  • Investigate the effects of varying distances on magnetic field calculations
USEFUL FOR

Physics students, electrical engineers, and anyone interested in electromagnetic theory and the behavior of magnetic fields around current-carrying conductors.

Amaelle
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Good day All,
I have a confusion in my mind and i hope to clear it
biot.png

If we use the Amper law to calculate the magnetic field outside the cable, the value would be 0 because the electric current inside the amperian loop is equal to 0,
but in case we apply the Biot savart law to calculate the magnetic field say in the point B ( in red) i will use the principe of superposition and calulculate the magnetic filed generated by each current separatedly, but in this case because the distance varies, the magnetic field on B will not be 0
Any helps would be highly appreciated!
thanks
 

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You are likely not performing the integration correctly when using the Biot-Savart law. How are you setting up the integral?
 
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NFuller said:
You are likely not performing the integration correctly when using the Biot-Savart law. How are you setting up the integral?
yes you are right , thanks a lot for pointing this problem, my integral was a total mess
 
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