# Homework Help: Resistance of a wedge

1. Jun 25, 2013

### elionix

I'm interested in calculating the resistance of an object using the formula:

R=ρ (L/(T*W)) where L is the length and T*W is the cross sectional area.

My object is however, a wedge, so I do not know exactly how to calculate the resistance without doing an integral:

http://imageshack.us/photo/my-images/585/9evf.jpg/

Is this the proper approach? I'm having some trouble with the actual calculation of this... not sure if I'm setting up the problem correctly. Any help would be much appreciated!!

2. Jun 25, 2013

### Redbelly98

Staff Emeritus
Doing an integral is how I would calculate it. Is there some reason you do not want to use an integral?

3. Jun 25, 2013

### haruspex

It's not entirely clear which way you have wi and li. I assume it's intended to be consistent with l being the distance from wedge base to tip.
dl, yes, not dw.
You need to introduce a variable for the distance of an element from one end. I suggest taking it from the tip end and using x. (So an element thickness is dx, not dl.) What is w as a function of x?

4. Jun 25, 2013

### barryj

If you were measuring the resistance with an ohmmeter where would you touch the probes? At the tip and the center of the left base? I assume that there is no metal plate along the left edge, yes?

5. Jun 26, 2013

### haruspex

Well, I assumed the contact at the wide end was right across. However, there is a problem at the pointy end, as will be revealed by the integral.