Charge Q is distributed uniformly over a thin rod

[Evelima]

Charge Q is distributed uniformly over a thin rod...

Homework Statement

Charge Q is distributed uniformly over a thin rod of
lying along the x-axis between points (a,0) and (b,0)
as shown. Please answer each of the following
questions.

a) What is the linear charge density on the rod?
b) Find the electric field at the origin.

Homework Equations

linear charge density = Q / l
E = k Q / rˆ2

The Attempt at a Solution

This is what I got so far ...

dQ = lambda*dx = Qdx/(b-a)

integral of E = k dQ/rˆ2 i
= integral from a to b of k*lambda*dx/xˆ2 = k*lambda*(-1/b+1/a)

 

[Delphi51]

Looks good. You get a nicer looking answer for b if you drop the lambda and express it in terms of the given Q, a and b. Get a common denominator for that nasty 1/a - 1/b.

 

[supratim1]

yes, just proceed and replace lambda.