# RC Circuits with switch

• Engineering
• frutti

## Homework Statement

i need to find the Vs(t) and Vc(t)

http://img32.imageshack.us/img32/9071/circuiten.jpg [Broken]

## The Attempt at a Solution

since there is a switch i used two cases to find the Vc
one with switch on and switch off
switch on
http://img704.imageshack.us/img704/6180/switchon.jpg [Broken]
and switch off
http://img265.imageshack.us/img265/3259/switchoff.jpg [Broken]

but I am lost after this...
help me!

Last edited by a moderator:

## Homework Statement

i need to find the Vs(t) and Vc(t)

http://img32.imageshack.us/img32/9071/circuiten.jpg [Broken]

## The Attempt at a Solution

since there is a switch i used two cases to find the Vc
one with switch on and switch off
switch on
http://img704.imageshack.us/img704/6180/switchon.jpg [Broken]
and switch off
http://img265.imageshack.us/img265/3259/switchoff.jpg [Broken]

but I am lost after this...
help me!

The cap still needs to be there with the switch ON.

Write the KCL equation for the node at the top of capacitor (with the bottom of the cap being the common "ground" node), and solve the resulting differential equation, using the initial conditions from when the switch was open (assume the switch is closed at t=0). Show us your work, so we can help you more if you need it.

Last edited by a moderator: