Calculate R from Electric field lines.

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SUMMARY

The discussion centers on calculating the distance R from a point charge based on the electric field produced. The relevant equation is E = kQ/R², where E represents the electric field strength, k is Coulomb's constant, and Q is the charge. The user initially misinterpreted the relationship between electric field lines and charge, leading to an incorrect assumption about the equality of areas and strengths. After clarification, it was established that the charge Q varies with the electric field lines, resolving the confusion.

PREREQUISITES
  • Understanding of electric fields and point charges
  • Familiarity with Coulomb's law and the equation E = kQ/R²
  • Basic algebra skills for solving equations
  • Knowledge of electric field lines and their representation of field strength
NEXT STEPS
  • Study the concept of electric field lines and their relationship to charge density
  • Learn about the implications of varying charge in electric field calculations
  • Explore additional examples of point charge problems in electrostatics
  • Review online resources or tutoring platforms like Cengage for further assistance
USEFUL FOR

Students studying physics, particularly those focusing on electrostatics, as well as educators seeking to clarify concepts related to electric fields and point charges.

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1. The problem statement
The electric field E (arrows) is produced by a point charge. Find R in meters
physpic.jpg


Homework Equations


E(due to pt charge) = kq/R^2
# of field lines/unit area represents relative field strength (only statement in my notes that seems to apply to problem)


The Attempt at a Solution


I assumed the two areas are equal, and the relative strengths are 5Q and 2Q, respectively. Then, k5Q/(1.5)^2 = k2Q/R^2 I solved and got .77, and neither .77 or 1.5+.77 are answer choices so I am obviously wrong. This problem is obviously supposed to be very easy since it is the first one on my practice test but it is nothing like anything in the book or examples done is class so I am clueless.
 
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If anyone knows where to start on this problem or can point me in the right direction, it would be greatly appreciated. I have access to online tutoring through cengage and two tutors were unable to help me with it so I am getting desperate.
 
Q is the same for both distances. It is the electric field, E=kQ/r^2 which is E=5 for r=1.5 and E=2 for r=R.

ehild
 
Last edited:
Thank you! My notes have Q varying with the amount of electric field lines, which is where I was mistaken. The problem makes sense now
 

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