Mag. component of positive charges

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Discussion Overview

The discussion revolves around deriving an expression for the force between two equal positive charges traveling in the same direction, incorporating both electrostatic and magnetic components. The focus is on theoretical approaches and mathematical reasoning related to electromagnetic interactions.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant presents a problem involving two equal positive charges and requests assistance in deriving a specific force expression.
  • Another participant suggests three approaches: calculating the magnetic field from one charge at the location of the other and using the Lorentz force, applying Lorentz transformations in a moving frame, or calculating forces in the moving frame and transforming to a stationary frame.
  • A participant hints at using the Biot-Savart law to relate the magnetic field to the problem, suggesting a substitution of terms based on the given data.
  • Further contributions discuss the relationship between current, charge, and time intervals to derive the magnetic field.
  • Another participant emphasizes the importance of determining the direction of the magnetic field and how to calculate the magnetic force using the vector cross product.
  • One participant suggests integrating all forces to arrive at a solution, implying a more complex mathematical approach may be necessary.

Areas of Agreement / Disagreement

Participants present multiple approaches to the problem, indicating a lack of consensus on the best method to derive the desired expression. The discussion remains unresolved with various viewpoints on how to proceed.

Contextual Notes

Participants express uncertainty about connecting the derived magnetic field to the required force expression and the implications of integrating forces. There are also dependencies on definitions and assumptions related to the magnetic field and force calculations.

buddingscientist
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Hello scientists,

I'm unable to make any advances with this small problem.. two equal and positive charges (q) travel (in the same direction) at a speed (v), and are parallel to each other, at separation (r).
Derive an expression for the force between them, in the form of:
F = Felec(1 - [correction term]).
If anyone could shed some light on this or provide some insight it would be great thanks
 
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There are three approaches you might try:

(a) Calculate both the magnetic field due to one of the charges at the location of the other charge then calculate the Lorentz force (electrostatic plus v cross B).

(b) Calculate the static electric field in a frame of reference moving along with the charges and then use the Lorentz transformation to find the electrostatic and magnetic fields in the stationary frame of reference.

(c) Same as (b) except you calculate the force in the moving frame and the use the Lorentz transform to find the force in the stationary frame.

I suspect you're interested in (a).
 
Hmm thanks for the notes,
I get hints that I should use the Biot-savart law B = (mo/4p)(I.dL/r2) (m = mu, p = pi), and replace I.dL with data given in the question
 
Sounds like a great start!
 
I'm still having some trouble relating the two :(
 
Think of the current as charge divided by a time interval and L as the speed times the time interval. The time interval will cancel out and you should get your magnetic field.
 
Well..
B = (mo/4p)(qv/r^2)
I'm unfamiliar with how to connect it with 'F = Felec(1 - [correction term])'

Thanks a lot for the ideas and help by the way
 
If you learned about Biot-Savart then you should be able to determine the direction of the magnetic field. The magnetic force will be q v X b (vector cross product) which you will find is along a vector connecting the two charged particles (be careful with the signs). Finally, just add the electrostatic force.
 
take all forces in account, calculate them using integration (calculus).
I think answer is come with it.
 

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