Calculate R from Electric field lines.

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Homework Help Overview

The problem involves calculating the distance R from a point charge based on the electric field produced by that charge. The context includes the relationship between electric field strength and the number of field lines per unit area.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between electric field strength and distance from a point charge, with one participant attempting to equate relative strengths based on field lines. Others question the assumptions made about the charge and field strength.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. One participant has expressed confusion about the relationship between charge and electric field lines, while another has clarified that the charge remains constant for both distances.

Contextual Notes

There is mention of varying interpretations of the charge based on electric field lines, which has led to some confusion. Additionally, the problem's difficulty level is noted, as it is the first question on a practice test, but does not align with previous examples from class or the textbook.

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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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