#### tinhnho

Joined Aug 31, 2004
34
hi everyone

The voltage source in the figure below has a step increase at t =0 . For t<0, vs(t)=0 while for t>0, vs(t) = 1V
Find v1(0-), v2(0-), v1(0+), v2(0+), v1(infinite), v2(infinite)

i have found v1(0-)=0 and v2(0-)=0 , but just confuse how to find v1(0+), v2(0+), v1(infinite), v2(infinite), could anyone please give me some ideas ? thanks alot

#### Attachments

Joined Jan 19, 2004
220
at 0+, the caps act like shorts while inductors acts like open ckts.... therefore the ckt reduces to a voltage divider of R1&R3.. v1=v2=0.5V

at t=infinite, the caps are open, the inductors short, the V2=0
and v1=0.6666V

jus verify the answers of u hav em

#### tinhnho

Joined Aug 31, 2004
34
VEry thanks for those comments. Sorry that i still have other question which just like to verify with you. Please see these pictures below

Question:

The current source in the figure below has a step increase at t =0 . For t<0, Is(t)=0 while for t>0, is(t) = I0. The circuit is "dead" before t = 0, so v(0-)=Ic(0-)=Ir(0-)=iL(0-)=0

a) Find v(0+), Ic(0+), Ir(0+), IL(0+), Symbolic answers( formulas)

B) Find dv/dt at t =0 symbolic answer( formulas)

Here is the answer for both a) and b) in the picture number 2 from left to right

#### Attachments

Joined Jan 19, 2004
220
i think
ic(0+)= Is, Ir=0, Il=0...ie the cap acts like short
why do u say Ic=-Is??
V(0)=0
V=C*(integral)Ic(t)dt
dv/dt eludes me

#### tinhnho

Joined Aug 31, 2004
34
sorry, i think they were
Ic = C(dv/dt)
Ir= -Is

now it's confusing me 