Direction of force on a voice coil

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SUMMARY

The discussion focuses on the direction of force on a voice coil in relation to the magnetic field and current. When the conductor is straight, determining the force direction is straightforward. However, for curved surfaces, the force direction is determined by the tangential orientation at each point. Specifically, at position 1, the force is zero due to parallel current and magnetic field, while at position 2, the force is directed to the right due to perpendicular alignment. The force direction at position 3 is also towards the right but not entirely so, emphasizing the importance of the relative orientation between current (I) and magnetic field (B) in a cylindrical coordinate system.

PREREQUISITES
  • Understanding of electromagnetic principles, specifically Lorentz force law.
  • Familiarity with cylindrical coordinate systems.
  • Knowledge of voice coil mechanics and operation.
  • Basic concepts of magnetic fields and current interactions.
NEXT STEPS
  • Study the Lorentz force law in detail to understand force direction calculations.
  • Explore cylindrical coordinate systems and their applications in electromagnetism.
  • Research the mechanics of voice coils and their role in audio devices.
  • Examine the effects of varying current and magnetic field orientations on force direction.
USEFUL FOR

Electronics engineers, audio engineers, physics students, and anyone involved in the design or analysis of electromagnetic devices, particularly those utilizing voice coils.

Physicslearner500039
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TL;DR
Want to find the direction of force on a voice coil due to magnetic field
I want to understand the direction of force on the voice coil, if the conductor is straight line it is easy to find the force direction. In the case of the diagram i shown below, for the curved surfaces i should take tangential to the surface at every point. Am i correct? So for position 1 since ##I## and ##\vec B## are parallel, the force due to Pos1 will be 0. For Pos2 since Current and B are perpendicular the direction is to the right. For Pos3 it is little confusing, it is towards right (not completely). Does the direction of force change if the voice coil is aligned differently? I think it is the relative orientation between ##I## and ##\vec B## that matters?
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You must think in a cylindrical coordinate system.
The circular current in the coil is everywhere perpendicular to the radial magnetic field. The force is therefore always in the axial direction, that is perpendicular to both the magnetic field and current.
 

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