- #1
BlackWyvern
- 105
- 0
Homework Statement
What would the electrical resistance of a paraboloid from y = 0 to L be?
Homework Equations
[tex]R = \rho \frac{L}{A}[/tex]
The Attempt at a Solution
Okay, so I'll put the parabola (that would rotate into the paraboloid) into the form [tex] y = \sqrt{x}[/tex]
The function A(x) is just the area of the circle, at distance x.
A = [tex]\pi y^{2} = \pi x[/tex]
I'll break the paraboloid up first into a finite sum of discs, from 0 to L.
[tex]R = \Sigma \rho \frac{\Delta x}{A(x)}[/tex]
==>
[tex]R = \int^{L}_{0} \rho \frac{dx}{\pi x}[/tex]
==>
[tex]R = \frac{\rho}{\pi} \int^{L}_{0}\frac{1}{x} dx[/tex]
This integral resolves to:
[tex]R = [\frac{\rho}{\pi}ln(x)]^{L}_{0}[/tex]
Natural log of 0 is undefined, so this would resolve to a numerical answer, as at the limit of x ==> 0, the area approaches zero and this means infinite resistance. But is the maths correct? Or can someone suggest a better way to actually find an answer.