How Is Work Calculated When Changing Orbital Radius in an Electric Field?

AI Thread Summary
The discussion focuses on deriving the work done by an external agent when increasing the radius of a charged particle's circular motion in an electric field. The key formula mentioned is W = (Qq/8πε₀)(1/r1 - 1/r2), which relates to the potential energy change due to the shift from radius r1 to r2. Participants highlight the importance of calculating both kinetic and potential energy, with a specific emphasis on understanding the factor of 8 in the equation. Clarification is sought on the derivation process, particularly how to incorporate potential energy into the calculations. The conversation aims to resolve confusion surrounding these concepts in electrostatics.
jperk980
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A particle of positive charge Q is fixed at point P. A second particle of mass m and negative charge -q moves at constant speed in a circle of radius r1, centered at P. Derive an expression for the work W that must be done by an external agent on the second particle to increase the radius of the circle of motion to r2. (Use epsilon_0 for 0, r1 for r1, r2 for r2, and Q, m, and q as necessary.)
I know the answer to be (Qq/8pi*episolon_0)(1/r1-1/r2)
I know that i use the equation w=k*q1q2/r and i believe r to be (1/r1-1/r2). I do not understand how to get 8 though could someone please help!
 
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TE= KE+PE
you forgot calculate the PE
increase the radius = change of TE
 
jperk980 said:
I know that i use the equation w=k*q1q2/r and i believe r to be (1/r1-1/r2). I do not understand how to get 8 though could someone please help!

Show your calculations briefly so that we can take it up from there.
 

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