Electric Field as a function of r, evaluating bounds

[guyvsdcsniper]

Homework Statement

A sphere with radius R has a volume charge density
ρ = ρ0 𝑟⁄𝑅, where ρ0 is constant.

Find the electric field as a function of r, from r=0 to infinity.

Relevant Equations

Eda=qenc/epsilon

Im having trouble understanding the wording to this problem. When it says "from r=0 to r=infinity". My Qenc would zero out. I guess it makes sense that from infinitely far away you wouldn't "feel' the electric field but considering this question leads to 4 other questions I don't think I am approaching this right.

Can anyone help me understand this a little better?

 

[BvU]

My Qenc would zero out

What do you mean with that ?
$Q_{\rm enc}$ is zero for $r=0$ only. It increases with $r$ until $r=R$ and then it stays the same -- all the way.

 

[guyvsdcsniper]

What do you mean with that ?
$Q_{\rm enc}$ is zero for $r=0$ only. It increases with $r$ until $r=R$ and then it stays the same -- all the way.

I was referring to integrating the r on the last step of my work.

But i think i understand what the question is really asking based off what you said. I am basically evaluating the electric field at r=0, r=R ? Past R the electric field is constant.

But what would my limits be for the r component of Qenc?

 

[SammyS]

I was referring to integrating the r on the last step of my work.

But i think i understand what the question is really asking based off what you said. I am basically evaluating the electric field at r=0, r=R ? Past R the electric field is constant.

But what would my limits be for the r component of Qenc?

The electric field is not constant for r > R, rather $Q_\text{Enc}$ is constant for r > R .

You need to integrate the charge density to find the charge enclosed within a sphere of radius r, where
0 < r ≤ R .

 

[guyvsdcsniper]

Sorry, I think the wording just completely threw me off. I understand what the questions is asking now. I just confused myself really bad.