Re: Series-Parallel DC RC circuit

On Sun, 08 Mar 2009 18:11:24 -0700, Dan Coby <adcoby@xxxxxxxxxxxxx>
wrote:

Bob Engelhardt wrote:
bg wrote:
The capacitor charges through the series resistor but discharges
through the
parallel equivalent of the two resistors. All the shunt resistor does is
divide the source voltage, so that the cap voltage will never equal the
source voltage. ...

No no no. The shunt resistor also divides the charge /current/, so the
capacitor charges more slowly. The Thevenin equivalent is the
appropriate approach.

Bob

A little bit of nit picking: Actually the capacitor charges FASTER
to a lower voltage. The thevenin equivalent resistance gives a smaller
time constant which means a quicker initial increase in voltage. The
final voltage will be the thevenin voltage which is lower since the
two resistors form a voltage divider.

The initial slope of the capacitor charge, measured in volts/second,
is independent of R2 (for nonzero R2 of course). It's just

dv/dt = V1/(R1*C)

John

.

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