## Time variant RC and RL circuits

Ok so I have some topic overview questions. I think I am on the right track but would like to make sure I am thinking about this the correct way.

When I say time variant I simply mean there is a simple switch in the circuit. This is link to a were I found my supplemental material and it has a switch like I am talking about. http://www.allaboutcircuits.com/vol_1/chpt_16/2.html

Question 1:
Under what conditions does a Capacitor act like (A) an open circuit? (B) a short circuit? (C) a voltage source?

Question 2:
Under what conditions does an Inductor act like (A) a short circuit? (B) an open circuit? (C) a current source?

1a) at t=0-
because initially fully discharged thus empty and open circuit

1b) at t=0+
because the V across would be 0 thus short circuit

1c) at ∞
because capacitors remember/store voltage thus voltage source

2a) at t=0-
because initially like nothing is there thus short circuit

2b) at t=0+
because the I across would be 0 thus an open circuit

2c) at ∞
because inductors remember all current sources thus would act like a current source

When we look at initial-final response equations:
y(t)=yF + (yi - yF)e-t/τ
yi=y(0+)
yF=y(∞)
τ= RC or L/R depending on the circuit

3) How do you find y(0+) for a capacitor?
4) How do you find y(0+) for current through an inductor?
5) How do you find y(0+) for voltage on a resistor?
6) How do you find y(∞)?

I do not know the answer to 3-6. I am obviously kind of confused when it comes to the addition of the on/off switch into the circuit network.

HELP on the 0+, 0- and ∞ times would be great!

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