Measuring capactitance

[Mark S.]

Have i got this correct.

capactitance = eA/d

e = Permittivity of dielectric.
A = Area of plate overlap in square metres
d = Distance between plates in meters.

So, a capacitor, consisting of two parallel metal
plates of overlapping area 20 cm², 10 mm apart, with a mica
dielectric, has a capacitance of:

e = 6 * 9 * (10-12)
d = 0.01 (10mm or 1cm)
A = 0.20 (20cm²)

In my book it says 20cm² is = 0.002 instead of 0.2

Am i missing something here?

How does 20cm² become 0.002 . I thought that would mean 2mm².

Thanks Mark S.

 

[Hero999]

Suppose I have a strip of paper 1cm by 20cm, now I'll calculate the area in both cm² and m²

cm²
1*20 = 20cm²

m²
Now:
1cm = 0.01m
20cm = 0.2m
so:
0.01*0.2 = 0.002m²

See what I mean?

 

[Mark S.]

Thanks for that Hero999 . Now i get it