# voltage drop

#### myoplex11

Joined Oct 3, 2007
5
A 6V DC voltage source is connected across both a 5kohm resistor and a 10 nF capacitor in series. The voltage drop across the resistor is what?

#### Dave

Joined Nov 17, 2003
6,970
v(t) = V*exp(-t/RC)

V = voltage at source
R = resistance
C = capacitance

Dave

#### myoplex11

Joined Oct 3, 2007
5
thanks but the time is not given

#### Dave

Joined Nov 17, 2003
6,970
thanks but the time is not given
From the above equation the voltage across the resistor is a function of time, so it is pretty essential to the question - could it be asking you for the initial or final voltage across the resistor?

Dave

#### myoplex11

Joined Oct 3, 2007
5
it is the final voltage across the resistor

#### Dave

Joined Nov 17, 2003
6,970
it is the final voltage across the resistor
For the final voltage, and in the absence of a specific time, in the above equation use t = $$\infty$$, therefore you get:

v(t) = 6*exp(-$$\infty$$)

exp(-$$\infty$$) = 0, therefore in this ideal scenario the voltage across the resistor is 0V, i.e. the entire source voltage is across the capacitor.

Dave