Electric field strength -- calculating distance from charge

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SUMMARY

The discussion focuses on calculating the distance from a long uniform line of charge where the electric field strength changes from 1000 N/C to 4000 N/C. The relevant equation for the electric field of a line charge is E = (2kλ)/r, where λ is the linear charge density. The user initially attempted to use E = kq/r², which is incorrect for this scenario. The correct approach shows that the distance is inversely proportional to the electric field strength, leading to the conclusion that the distance must be one-fourth of the original distance to achieve the increased field strength.

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  • Understanding of electric field concepts, specifically for line charges.
  • Familiarity with the equation E = (2kλ)/r for electric fields.
  • Knowledge of linear charge density (λ) and its significance.
  • Basic algebra skills for manipulating equations.
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  • Learn about linear charge density and its calculation methods.
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Iron_Man_123
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Homework Statement


At a distance D from a very long (essentially infinite) uniform line of charge, the electric field strength is 1000 N/C. At what distance from the line will the field strength to be 4000 N/C?

Homework Equations


E=kq/r2

The Attempt at a Solution


I know that E is inversely proportional like so: E~1/r2
hence by rearranging for 'r' I got: r~sqrt(1/E)
then I plugged in 4E because 4000 N/C is four times 1000 N/C: r~sqrt(q/4E)
and I got r~E/2 but the answer is E/4 and I don't know how?

Thanks in advance
 
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HI,

You want to develop an expression for the electric field of a long line charge first. Your relevant equation doesn't fit that.
 
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What is the relevant equation that fits this scenario then?
 

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