I've gone through school and done all the work but looking back at it i still don't quite get it.
The rule is current in a capacitor leads and in an inductor lags. The inductor makes perfect sense but the capacitor doesn't.
We live in a causal world. Nothing from the future can affect the present. That said the inductor lags but then why does the capacitor not lag even more?
Is this only a mathematical construct?
Best Answer
To use terms like lead or lag is to imply that your are refering to the AC sinusoidal analysis of capacitors and inductors and that means the steady state AC situation in which currents can lead voltages or voltages can lead currents. Lead or lag does not imply transient analysis.
Go back to the basic formula for a capacitor Q = CV. Then differentiate both sides to get dQ/dt = C dv/dt and of course dQ/dt = current so: -
\$I = C \dfrac{dv}{dt}\$
If voltage rises at a certain rate the current will be constant - nothing to do with leading or lagging here until you apply a sinewave and the differential of a sinewave voltage is a cosine wave hence current leads voltage by 90 degrees BUT we're taling steady state AC analysis and that's when the terms leading and lagging apply - they don't make sense when talking about transient analysis.