(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The radius r of a wire of length L increases according to r = a * exp(bx^2), x is the distance from one end to the other end of the wire. What is the resistance of the wire?

2. Relevant equations

[itex]R =\frac{L * \rho}{A}[/itex]

3. The attempt at a solution

[itex]dR =\frac{dx * \rho}{A}[/itex]

[itex]A(r) = \pi * r^2[/itex]

[itex]r(x) = a* e^{bx^2}[/itex]

[itex]A(x) =\pi a^2 * e^{2bx^2}[/itex]

[itex]R =\int^{L}_{0}\frac{\rho}{\pi a^2 * e^{2bx^2}}*dx[/itex]

Two questions

First of all. Is this approach correct? And second, how does one integrate an errorfunction? (Of course one can use WolframAlpha but how does one get this solution?)

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Resistance of a wire with changing radius

**Physics Forums | Science Articles, Homework Help, Discussion**