Force on current carrying conductor

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SUMMARY

The discussion centers on the force experienced by a current-carrying conductor in a magnetic field, specifically addressing the constant of proportionality, k, in the equation F = kILBsin(θ). In SI units, k is defined as 1, simplifying the equation to F = ILBsin(θ), where F is the force, I is the current in Amperes, L is the length in meters, and B is the magnetic field strength in Teslas. This definition allows for a direct interpretation of the force acting on a wire carrying 1 Amp of current at a right angle to a 1 Tesla magnetic field, resulting in a force of 1 Newton. The discussion also highlights that different unit systems would require adjustments to the value of k.

PREREQUISITES
  • Understanding of electromagnetic principles, specifically the Lorentz force law.
  • Familiarity with SI units, particularly the definitions of Ampere, Tesla, and Newton.
  • Basic knowledge of trigonometric functions, especially sine.
  • Concept of proportionality constants in physics equations.
NEXT STEPS
  • Explore the derivation of the Lorentz force law in different unit systems.
  • Study the implications of using non-SI units in electromagnetic calculations.
  • Learn about the applications of the Tesla unit in various electromagnetic contexts.
  • Investigate the role of angles in force calculations involving magnetic fields.
USEFUL FOR

Physics students, educators, and professionals in engineering fields who require a solid understanding of electromagnetic forces and unit systems.

uzair_ha91
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I found this sentence in my textbook very confusing:

"...where k is constant of
proportionality. If we follow SI units, the value of k is 1."
Thus in
SI units, F=kILBsin<theta>=ILBsin<theta>

Why is the value of k taken as 1 only because we're following the SI units?
 
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Set k = 1 allows you to define the Tesla in SI units. If a wire is carrying a current of 1 Amp and is 1 metre long and is orientated so the direction of current flow is 90 degrees to a magnetic field of 1 Telsa then the force acting on the wire will be 1N. The sin theta bit is for when the current or moving charge is at any other angle than 90 degree to the magnetic field direction.
 
uzair_ha91 said:
Why is the value of k taken as 1 only because we're following the SI units?
Systems of units are set up to make the fundamental equations simpler. (SI Units are not the only system of units.)

You would agree, I trust, that if you measured the length in units of one-half meter (instead of the usual meter), you'd need to modify that force equation by choosing a different constant of proportionality? (k = 1/2)
 

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