- #1
anthonuc
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Homework Statement
I want to find ix in the circuit below when the switch opens at t=0 after having been closed for a long time.
Homework Equations
v(t) = v(infinity) + (v(0)-v(infinity))e-t/RC
i(t) = C dv(t)/dt
ix = isource - i(t)
v(t) = voltage across capacitor
i(t) = current through capacitor
The Attempt at a Solution
I just need to find v(t) then i(t) then ix using the equations I have.
I transformed the circuit so that the current source and resistor in parallel become a voltage source and resistor in parallel. The voltage source = 4mA * 2kOhm = 8 V
v(infinity) = 8V
My only real problem:
v(0) = ?
When the switch is closed, how is the circuit affected? Seems so trivial but I'm really confused as to what happens to the circuit at t=0 and finding v(0).
When the switch opens it's easy - a simple RC circuit. But I'm having a hard time understanding what happens to the circuit while the switch is closed. My guess is all the current goes through the short closed switch and v(inifinity) = 0?
[PLAIN]http://sphotos.ak.fbcdn.net/hphotos-ak-ash2/hs399.ash2/67756_10150101801434992_712009991_7559768_7479272_n.jpg
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