Resistance of a Circular resistor

[jgrant333]

Hello all.

I'm trying to calculate the resistance of a circular resistor with the following specifications:

Doped Silicon with a carrier concentration of 1.6x1025 m-3 (sheet resistance ~ 0.5 ohms/square)

Radius = 200 microns
thickness = 5 microns.

I know the general formula for calculating resistance of a standard serpentine configuration:

Resistance = (resistivity/thickness) x Length/Width
= sheet resistance x (Length/Width)

However what is the formula for a circular resistor?

 

[Ouabache]

It seems the point of this question, is to get you to think how would you calculate resistance of a shape that is not rectangular.
To make the calculation easier, they gave you a regular geometric shape.
Between what two points are you basing resistance of this shape?