modified 9 years ago

AC current and voltage of capacitor

00:55:55

Art of Electronics 3rd ed. 1.7.1 Frequency analysis of reactive circuits

green: current I(t)
blue: voltage

Current as a function of time:
  I(t) = C*dV/dt = C*ω*V₀*cos ωt

  The phase of current leading the input voltage by 90°

Amplitude only:  I = V/ (1/ωt)
where   ω = 2*π*f 

R = 1/ωC

For example a 1μF capacitor put across the 115V (rms) 60Hz powerline draws a current of rms amplitude:

I = U/R

I = 115V / (1/ 2*π * 60 * 10⁻⁶F) = 43.4mA (rms)

published 9 years ago

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