A square with charges and an electric field

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SUMMARY

The discussion revolves around calculating the electric field at the origin due to a square arrangement of charges in a physics problem. The participant utilized the formula E = kq/r^2 to determine the electric field from charge 1, concluding that its value is E1 = -12.4 V/C, split into components as E1 = -4.61i - 11.51j. The participant proposed that charge 3 (q3) should be -10e-9 C to counterbalance the electric field from charge 1. Feedback from another participant confirmed the validity of this approach and emphasized the importance of selecting charge 4 (q4) appropriately to achieve cancellation.

PREREQUISITES
  • Understanding of electric fields and Coulomb's law
  • Familiarity with vector components in physics
  • Knowledge of charge interactions in electrostatics
  • Ability to apply the principle of superposition for electric fields
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  • Study the principles of electric field superposition in electrostatics
  • Learn how to calculate electric fields from multiple point charges
  • Explore the concept of electric field lines and their implications
  • Investigate the effects of charge placement on electric field strength and direction
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Students in physics, particularly those preparing for exams involving electrostatics, as well as educators looking for practical examples of electric field calculations.

Melawrghk
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Homework Statement


This is a problem from my physics midterm. I have no idea whether I got ANYTHING at all right in it, although I certainly hope so.
physmt1.jpg


Homework Equations


E = kq/r^2

The Attempt at a Solution


Okey dokey. I was running out of time (majorly) so I figured I'd only look at charge 1's electric field at the origin. The main theory (or something like that) behind it was that charges 2 and 4 lay in a line, so their electric fields would coincide, so charge 4 could be used to cancel out 2's effects.
I then decided that charge 3 basically has to counterbalance charge 1's electric field. So I found 1's electric field at the origin:
E1 = (k*10e-9)/7.25 = -12.4V/C
I then split it into components, x & y, because that is what charge 3 would have to counteract.
E1 = -4.61i - 11.51j

Long story short, I arrived at the conclusion that q(3) should be -10e-9 C. But I'm not sure if that's at all right. Thoughts? Feedback?
 
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So you can choose Q4 as well as Q3?
I think your choice for Q3 is right on. The combined E's due to Q1, Q2 and Q3 will be in the direction of Q4 so they can be canceled by choosing just the right Q4.
 
Yep, both q3 & q4 were unspecified. The question only asked about q3 though.
Thanks for the reply! :) That makes me feel a little better about my overall predicament.
 

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