# Material Thickness

1. Dec 16, 2009

### Kev1n

1. A conductive sheet of material has a CSA of 10mm x 20mm. Reisistivity of 103 (10 to the 3, 10,000) ohms M. Calculate thickness of the material required to give resistance of 5k ohms

2. Ro = RA/l , where l would be thickness, l = RA/Ro

3. Thickness = 5,000 x 0.2 / 10,000 = o.1m therefore 100m

2. Dec 16, 2009

### Redbelly98

Staff Emeritus
There are some problems with your calculation:
103 is not 10,000.

The area is not 0.2 (is that supposed to be in m2?). Try converting the mm values to meters first. Remember, 1 mm is 10-3 m.​

3. Dec 18, 2009

### Kev1n

Thanks:

Thickness = 5,000 x 0.0002/ 1,000 = 1 x 10-3m therefore 1mm

or do I have to sq the .ooo2 giving:

=5,000 x 4x10-8 / 1,000 = 2 x 10-7

4. Dec 18, 2009

### Redbelly98

Staff Emeritus
One of those is correct! Here are 2 questions to help you decide which:

1. How did you get the 0.0002 value for the area, and therefore what are the units associated with this value?

2. Are these units (from my previous question) correct units for an area, or would you need to square the units to to get an area?

Note: correct units for area can be expressed as m2, m·m, mm2, or mm·mm.

5. Dec 19, 2009

### Kev1n

Hi, thanks for the reply, think I am having a christmas moment.
The area should be 10mm x 20mm = 200mm in m 200 x 10-3 therefore 0.2m
Thickness = 5,000 x 0.2/ 1,000 = 1mm

How does this seem

6. Dec 19, 2009

### Redbelly98

Staff Emeritus