Question 1: why is the voltage of a capacitor as t goes to infinity equal to the voltage source?(adsbygoogle = window.adsbygoogle || []).push({}); This question has been answered. The steady state voltage is not simply equal to the voltage source.

Question 2:

So that does that mean voltage and current are always 90 degrees out of phase? I'm confused because I've done labs with RC series circuits where the voltage is only 20 degrees behind the current waveform for example. berkeman said:Just write the differential equations for voltage and current in the two situations.

V = L di/dt

I = C dv/dt

And remember that when you differentiate a sine wave, you get the cosine function. So current lags the voltage in an inductor, and voltage lags the current in a capacitor. Make sense?This question has been answered. They are only 90 degrees out of phase for purely capacitve or purely inductive circuits.

Question 3: According to this website, increasing the angular frequency causes the phase angle difference to increase in RC Parallel and RL Series circuits but it causes the phase angle difference to decrease in RC Series and RL Parallel circuits. Why is this? Why is the phase angle based on frequency?

Question 4: According to the this PDF, for this circuit:

http://i.imgur.com/dqjdjaf.png

the following equations apply:

http://i.imgur.com/8GUZF9D.png

Also, for this circuit:

http://i.imgur.com/dcrG29t.png

the following equations apply:

http://i.imgur.com/2WYQDsH.png

How would I derive those equations? The only equation I was given was this one:

$$v(t)=\begin{cases} v(0), & t<0 \\ v(\infty )+(v(0)-v(\infty )){ e }^{ -t/\tau }, & t>0 \end{cases}$$

and I wondering if it's possible to derive those equations from the above equation I was given.

Question 5: Is the below correct?

When a capacitor is charging, the capacitor’s voltage is at 63% and increasing when t=τ

When a capacitor is charging, the resistor’s voltage is at 37% and decreasing when t=τ

When a capacitor is discharging, the capacitor’s voltage is at 63% and decreasing when t=τ

When a capacitor is discharging, the resistor’s voltage is at 37% and increasing when t=τ

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# A couple of questions about RC and RL Circuits

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