Electric Field at Point Z, Two Charges

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SUMMARY

The discussion focuses on calculating the electric field at point Z due to two charges, utilizing the formula epsilon = Fe/q. The participant initially miscalculated the electric field strength, arriving at 1.44 x 10^5 N/C instead of the correct value of 1.21 x 10^5 N/C. Key errors included confusion between sine and cosine functions for angle calculations and neglecting to square root the radius components. Ultimately, the participant corrected their approach by properly applying trigonometric functions and recognizing the relationship sin(180-theta) = sin(theta).

PREREQUISITES
  • Understanding of electric field concepts and calculations
  • Familiarity with trigonometric functions, specifically sine and cosine
  • Knowledge of vector components in physics
  • Proficiency in using formulas related to electric forces
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  • Review the derivation and application of the electric field formula epsilon = Fe/q
  • Study trigonometric identities and their applications in physics problems
  • Learn about vector decomposition in two-dimensional physics problems
  • Explore common mistakes in electric field calculations and how to avoid them
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Students studying physics, particularly those focusing on electromagnetism, as well as educators looking for examples of common calculation errors in electric field problems.

mike_302
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Homework Statement



I have drawn the diagram on the attached page... IT contains all information. The question is simply to determine the electric field force at point Z (which is at the very upper edge of the page)



Homework Equations



epsilon= Fe/q


The Attempt at a Solution



scan0001.jpg


I just noticed I forgot to square root the radius (rAZ and rBZ) in the top right corner.. that changes my answer, but not to the right answer... Now I get 1.44*10^5 . Correct answer is 1.21*10^5

What's wrong :S
 
Last edited:
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I think it should be sin(90 - theta), not sin(theta)
 
woah... woah... why? tan(theta)=.04/.03 ... that's unarguable... that gives my radius...

And in the Y-component part, we are taught to use sin(theta) for Y-components, where theta is the angle from the positive x-axis.
 
Sorry, I confused sin with cos :S

Edit2: I keep getting 1.15 * 10^5
 
Last edited:
Figured it out... I dropped the sin(53.13) when I multiplied by 2... but to answer your question, sin(180-theta)=sin(theta)
 

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