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aftershock
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Homework Statement
There are 2 coaxial cylindrical conductors. The inner cylinder has radius a, while the outer cylinder has radius b. There is no charge in the region a < r < b. If the inner cylinder is at potential Vo and the outer cylinder is grounded, we want to find the potential in the region between the cylinders. We assume L >> b > a and neglect end effects.
a) Write Laplace's equation in cylindrical coordinates.
b) Assuming V(r) is a function of the axial distance r alone, integrate the differential equation and use the boundary conditions to find V(r) , a ≤ r ≤ b.
Homework Equations
∇2V = 0
The Attempt at a Solution
Laplace's equation in cylindrical coordinates would be
(1/r)(d/dr)(r*dV/dr) =0
Since there is no phi or z dependence. Also I know it's a partial and not d but I can't type the symbol.
To solve this
(1/r)(d/dr)(r*dV/dr) =0
(d/dr)(r*dV/dr) =0
r*dV/dr = C
dV/dr = C/r
dV = C/r dr
V = C*ln(r) + K , where C and K are constants.
Using the boundary conditions:
0 = C*ln(b) + K
Vo = C*ln(a) + K
and using that to solve for constants:
V = Vo/[ln(a/b)] * ln(r/b)
Is that right?