a question about the total charge on the curved surface

Status
Not open for further replies.
L

losheungwai

Newbie level 5
Joined
Sep 14, 2008
Messages
9
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,337
for a cylinder of radius 3 and height 5 given by x^2 + y^2 =9 and o<= z <=5
let the electirc charge density be proportional to the distance from the xy - plane.
find the total charge on the curved surfacae of the cylinder.

does it mean find the surface area of the curved surface of the cylinder???
 

Let the charge density be
ρ = k*r

then the total charge = ∫∫∫ρ*rdrdθdz =k* ∫∫∫r^2drdθdz
where limit of integration on r is 0 to 3, on θ from 0 to 2Π, and on z from 0 to 5.
 

but what is k?
does that mean the answer is something k?

Added after 5 minutes:

but isn't this equation for volume of a cone??
 

Yes, you said the question contains, the charge density is proportional to distance from axis in the x-y plane. Unless you know the proportionality constant, how do you find a numerical answer?
 

I am sorry, I did not go through the question thoroughly. It is not the right integration i mentioned there. I thought the charge increases radially. But the question contains variation of charge with height, so accordingly the equation has to be changed.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…