All this talk of electrical matters reminds me of the first formula
I learned after V = I R (one of the three Laws of Ohm). It was:
K A
C = 0.224 ----- (n-1)
d
where
C = capacity in mmf
K = dielectric constant
A = area of each plate in square inches
d = distance between plates
n = number of plates in the condenser
and
capacity = capacitance
mmf = pF
condenser = capacitor
I was about twelve years old when I learned it and I still remember
it. Did anyone out there ever buy stuff from an ad in CQ or QST for
Joe Palmer Surplus Electronics in the '50s or '60s? He's my father.
We used to salvage power pole transformers ("pole pigs") for power
supplies, bathing in PCBs up to our armpits without expiring, and
in earlier days my father made condensers from "tinfoil" and window
glass, though that became unnecessary after the war.
Does anyone get into physics through amateur radio these days?