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Monthly Archives: May 2011

Finish this thought later, but a capacitor is like filling up a balloon, it resists current flow when the capacitor is full.

The equation talks about “the rate of change of charge” (ie the CURRENT) is equal to

dq/dt + q/RC = V/R

I(t) = Vs/R – q/RC

Where Vs is the voltage of the source, and q/RC is a measure of how much charge is on the plates so far.

That means the current is SLOWING DOWN as the difference between (VoltageSource/R – charge stored) becomes smaller.

and an inductor is like kinks in a hose (slows down change in current flow).

dI/dt + I R/L = V/L

LdI/dt + I R = V

Which means the rate of change of CURRENT is
dI/dt = V/L – I R/L

Ie the rate of change of current is going to depend on CURRENT CURRENT, so like how fast it changes, depends on how much current is already flowing. The inductor slows down RATE OF CHANGE OF CURRENT because the higher the inductance L, the lower dI/dt is.

Its annoying how they hide these, but they’re all available on the web.