Calculating Electric Field Strength from a Charged Wire

kmikias
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Homework Statement



The electric field strength 8.05 cm from a very long charged wire is 1310 N/C. What is the electric field strength (in N/C) 30.0 cm from the wire?

Homework Equations


E=F/Q
E=KQ/R^2


The Attempt at a Solution


First I try to find the charge using E=KQ/R^2
1320=K(Q)/(8.05)^2
Q= 9.432 x 10^-6

second I used the charge to find the electric field.
E= k(9.432 x 10^-6)/30^2
E= 94.32 N/C

I didn't convert cm to m because it would cancel out at the end.
so I don't know why my answer is still wrong.Any help will be great.
thanks guys.
 
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You are assuming the wire is a point charge, which it is not. You would have to integrate:
2 (Integral from 0 to infinity) kdq/r^2
I hope you know what to do from there
 
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