physical electronics formulas

λ (Wavelength) = c (The Speed of Light) / f (Frequency)



Capacitors

charge
Q = CV

Q := charge [coulombs]
C := capacitance [farads]
V := voltage [amperes]

Energy stored
E = 1/2 QV

E := energy [joules]
Time constant to change 1/e (charge/discharge)
t = RC
t := time in seconds
R := resistance [ohms]
e := natural number

reactance (resistance to AC current)
Xc = 1 / (2 Pi f C)

Xc := reactance [ohms]
Pi := pi
f := frequency [hertz]
C := capacitance [farads]


in series 1/C = 1/C1 + 1/C2 + ....
in parallel C = C1 + C2 + ....