Explaining F=BIl and F=Bqv for Many Charges

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    Electromagnetic Forces
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Discussion Overview

The discussion revolves around the relationship between the equations F = BIl and F = Bqv, specifically how they can be understood as equivalent expressions for the force on charges in a magnetic field. Participants explore the underlying principles and mathematical reasoning connecting these equations, considering both single and multiple charges.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that the equations can be related by considering a wire of length l carrying a net charge q with an average velocity v, leading to the expression F = BIl.
  • Another participant clarifies that the equations are part of the Lorentz Force Law and highlights the vector nature of the forces and currents involved, noting that the vectors are mutually orthogonal.
  • A different viewpoint is presented, stating that the current and velocity vectors do not necessarily need to be orthogonal to the magnetic field vector.

Areas of Agreement / Disagreement

Participants express different interpretations regarding the orthogonality of the vectors involved in the equations, indicating that there is no consensus on this aspect of the discussion.

Contextual Notes

The discussion does not resolve the implications of vector orientations in the equations and their effects on the force calculations.

poojarao
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Speed = distance/time and current = charge/time. Explain how F=BIl is actually the same equation as F= Bqv but considered for many charges in a group?

can someone please explain with working out please?

thanks
 
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Lets say that you had a wire with a length l. Let's say that traveling through that length is a net charge q, with an average velocity of v. v = distance/time, in which in this case, v = l/t. The current is I = charge/time = q/t. Therefore, F = B*q*(l/t) = B*(q/t)*l = BIl.
 
thanks a lot!
 
For clarity, these two equations (part of the Lorentz Force Law) are written as

F = l(I x B) = q(v x B)

where x indicates the cross product. meaning that the vectors F,I and B; or F,v,and B are all mutually orthogonal.
 
The I/v vectors need not be orthogonal with the B vector.
 

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