# Need help in step response circuit diagram

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1. Nov 19, 2016

### whatphysics

This isn't a homework question! I posted the question for context purpose.

So I understand that at t>0 the switch moves to b. Hence the first circuit diagram (pictured) I understand.

However for the 2nd circuit diagram (picture 2) when asked to transform to s domain. Why does this answer include the 10/s. To my understanding because the switch already switched to b, the 10V is no longer considered hence shouldn't be included as 10/s in the transformation circuit.

Can anyone explain this to me? Whether the answer key is wrong or are my concepts wrong?

Thank you so much in advance!!

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2. Nov 19, 2016

### cnh1995

The switch was at 'a' for a long time. So what is the voltage across the capacitor at t=0+?

3. Nov 19, 2016

### Delta²

As I can see from picture 1, it asks for the voltage V(t) for $t\geq 0$ so we are interested for the V(t) for t=0 too (not only for t>0).

4. Nov 19, 2016

### whatphysics

Ah that would make sense..thanks!

5. Nov 19, 2016

### whatphysics

Um 10V?

6. Nov 19, 2016

Yes.