Electric field between two charged rods

[aliaze1]

Homework Statement

Two 10-cm-long thin glass rods uniformly charged to are placed side by side, 4.0 cm apart. What are the electric field strengths at distances 1.0 cm, 2.0 cm, and 3.0 cm to the right of the rod on the left, along the line connecting the midpoints of the two rods?

Homework Equations

[1/(4??₀)] * {|Q| / [r* (r²+(0.5L)²)^0.5]}
the power "0.5" is the square root; √

The Attempt at a Solution

Calculating the charge @ 2cm seemed the easiest, so here is what I did:

L=0.1m
r=0.02m
Q=1*10^-8
1/(4??₀) = 9*10⁹

plugging these numbers in, I get 83562.90218, and since there are two rods, and this is equidistant from both, I added E_rod#1 + E_rod#2, which is the same as doubling the value, giving 167125.8044; incorrect

 

[learningphysics]

The two fields due to each rod are in opposite directions.

 

[aliaze1]

The two fields due to each rod are in opposite directions.

so their signs are opposite...thanks!

 

[Logbert]

This question is from section 27.3, Question 9 from the book "Physics for scientists and engineers second edition. A strategic approach" by Randall D. Knight, which is probably the most standard undergraduate physics text available and extremely good, and it even has answers for all the odd numbered questions.

I suggest reading your course material.