The Net Force on a Test Charge at Equilibrium Due to Two Point Charges

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    Coulomb's law Law
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Homework Help Overview

The problem involves determining the position on the x-axis where the net force on a small charge +q is zero, given two point charges: one positive and one negative, located at specified positions. The context is within electrostatics, specifically focusing on the forces between charged objects.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss equating forces exerted by the two point charges and the implications of charge positions. There is an exploration of the assumption that the test charge must be on the negative x-axis to achieve equilibrium. Questions arise regarding the cancellation of charge magnitudes in the force equations.

Discussion Status

The discussion is ongoing, with participants questioning the validity of their assumptions and the application of equations. Some guidance has been offered regarding the interpretation of variables in the force equations, but clarity on the cancellation of charges remains unresolved.

Contextual Notes

Participants are grappling with the implications of charge magnitudes and the setup of the problem, including the distances involved. There is a focus on ensuring that the correct charges are being considered in the equations used.

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Homework Statement


Two charges, one of 2.50 micro coulomb, and the other of -3.50 micro coulomb, are placed on the x-axis, one at the origin and the other at x=0.600m, as shown in Fig 21.36. Find the position on the x-axis where the net force on a small charge +q would be zero


Homework Equations


F= kq1q1/r^2


The Attempt at a Solution


I tried to equate the force when the distance of the two charges are 0.6m away to the force when the distance is x+0.6
 
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You can imagine that the charge has to be on the negative x-axis for the force exerted by the positive charge to equal the force exerted by the negative charge. Assume that it's a distance "d" from the origin; then it would be d+0.6 m from the other charge. Proceed from there.
 
yeah i have made that assumption by equating F1=F2, but, i don't understand what's happening after, i cancel my constants, and my charges should cancel so i end up with 1/(0.6)^2 = 1/(x+0.6)^2 , and u end up with 0
 
How do the charges cancel? One's 3.5 mC (in magnitude) and the other's 2.5 mC.
 
well i have F1=F2 so its kq1q2/(r)^2 = kq1q2/(r+6)^2
 
Don't apply equations without any thought. Think about what the letters in this equation:

kq1q2/(r)^2 = kq1q2/(r+6)^2

stand for. Assuming q1 is the test charge, do the q2's represent the same charge?
 
ideasrule said:
Don't apply equations without any thought. Think about what the letters in this equation:

kq1q2/(r)^2 = kq1q2/(r+6)^2

stand for. Assuming q1 is the test charge, do the q2's represent the same charge?

im sorry but i do not understand the last part, if we assume q1 is the test charge, so we are able to cancel q1 out?
 

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