- #1
Rijad Hadzic
- 321
- 20
Homework Statement
Two long concentric cylinders of radii .04 m and .08 m are separated by aluminum. The inner cylinder has a charge per unit length of [itex] \Lambda [/itex] at any time. When the two cylinders are maintained at a constant potential difference of 2 V via an external source, calculate the current from one cylinder to the other if the cylinders are 1 m long
Homework Equations
potential difference = IR
R = pl / A
I = dq/dt
J = I/A
J = neV
E = pJ
The Attempt at a Solution
So my first attempt I used:
potential difference = IR
(2 V ) / (R) = I
(R) = pl / A
length is 1 meter
I took area by pi(r)^2 outside - pi(r)^2 inside, pi(.08)^2 - pi(.04)^2 , .020 - .005 = .015 m^2
p is given in the book, p for aluminum is 2.655x10^-8
plugging in, R = 1.77 x 10^-6
so (2 V) / R = I
(2 V ) / (1.77 x 10^-6) = 1.1 x 10^6
But my answer is way off from my books, with the answer being: 6.8 x 10^8 A
What did I do wrong? I think the lambda at the beginning is a hint and that I might have to use Guass law??My next thought was:
E according to gauss law = (lambda)/(2pi\epsilon0r)
E/p = J
J * A = I
but how am I suppose to get a value for lambda?? sorry that part gets me mixed up :/
Can anyone comment on which method they think is leading me to the right direction? Also something I might be doing wrong??
Last edited: