Capacitors Marked in CMs

[Nick]

From the Radio & Television Engineers Reference Book, it's that 4*Pi again...

Confusing, isn't it! I believe this comes from a subtlety in the way the above text is presented.

The confusion arises because there are at least 4 different variants of CGS units, normalised in different ways. I believe that the book is using CGS-Gaussian units - the 4pi bit comes from Maxwell's equations and the definition used for a unit of charge in the Gaussian CGS system which has a factor of 4pi in it - the Coulomb Constant (in SI), Kc, is 1 / (4 x pi x Eo), which when factored out is 10e-11 x c^2

So both methods are correct (for CGS-Gaussian at least) ! In my calculations I used 3.1e10 cm-2 as the speed of light and took the dielectric constant of air to be 1 (its a tiny bit more) which is why the results are a tiny bit different.

Unit systems are horrid - the CGS system was a nightmare - at least SI makes sense.

My head now hurts and I need coffee...