# Micrometer reading/area of wire calculation

1. Jan 11, 2010

### Deliria

I measured the diameter of a wire and got 0.30. This is in millimeters right?

How would you calculate the cross sectional area? Is it just Πr²?

so Π x (0.15x10⁻³ x 0.15x10⁻³)
= 7.0 x 10⁻⁸m²

Is this right?

Last edited: Jan 11, 2010
2. Jan 11, 2010

### sjb-2812

Well, it could be 0.30 mm, but without further information it could just as easily be for instance 0.30 cm.

Assuming that the wire has a circular cross-section, then yes, your approach is right.

3. Jan 11, 2010

### Staff: Mentor

What is the exponent on 10 below? It looks like an accent mark, not a number.
Also, since your units are mm for the wire diameter, I think, why not leave the cross-section area in sq. mm.?

Last edited: Jan 11, 2010
4. Jan 11, 2010

### Deliria

Thanks for the help guys! :)

I'm pretty sure the diameter was in millimeters.

I couldn't fit it all in the answer box, lol. Standard form was the only way :(

5. Jan 11, 2010

### Staff: Mentor

Yeah, I meant mm, not cm. I edited these units in my previous post.