Potential energy for magnetic fields

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SUMMARY

The discussion centers on calculating the potential energy of a circular coil in a magnetic field. The coil has 10 turns, a radius of 0.05 m, and carries a current of 5 A, while the magnetic field is given as B = 0.05 T i + 0.12 T k. The correct formula for potential energy is U = -m·B, where m is the magnetic dipole moment calculated as I*A. The participant initially calculated U as -0.00511 J but later realized the correct value is -0.000472 J due to the need to account for the angle between the magnetic moment and the magnetic field, indicating the use of the dot product in the calculation.

PREREQUISITES
  • Understanding of magnetic dipole moment and its calculation (I*A)
  • Familiarity with vector dot products in physics
  • Knowledge of magnetic fields and their representation (e.g., B = Bxi + Bzk)
  • Basic principles of electromagnetism, particularly related to coils and currents
NEXT STEPS
  • Study the calculation of magnetic dipole moment in various configurations
  • Learn about the implications of the angle between magnetic moment and magnetic field
  • Explore advanced applications of the dot product in physics problems
  • Investigate the effects of coil turns and current variations on potential energy
USEFUL FOR

Students studying electromagnetism, physics educators, and anyone involved in electrical engineering or magnetic field applications.

jaejoon89
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Homework Statement



A circular 10 turn coil that has a radius of 0.05 m and current of 5A lies in the xy plane with a uniform magnetic field B = 0.05 T i + 0.12 T k (i and k are the unit vectors). What's the potential energy for the system?

Homework Equations



U = -m*B where m is the dipole moment = I*A

The Attempt at a Solution



B = sqrt((0.05 T)^2 + (0.12 T)^2) = 0.13 T

So for this I would get U = -0.00511 J, but the answer key says -0.000472 J... where's the mistake?
 
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I'm assuming from the answer that the magnetic moment must not be aligned with the field, but how do you know this given the problem? And how do you calculate this?
 
Well, we have to keep in mind that -m*B is actually a "dot product". ;)
 

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