Find Vc(0): Node Analysis & Ohms Law

[sammyqw]

Homework Statement

find Vc(0)

Homework Equations

Node analysis , ohms law

The Attempt at a Solution

Hi, I'm trying to find Vc(0). I used node analysis but I'm stuck in eq 1. I'll appreciate if someone can give me some suggestions. Thanks

 

[gneill]

Looks like you need to replace Vo with something. Go back to your schematic and see if you can express Vo in terms of the other quantities pertaining to the branch it's in.

 

[sammyqw]

Looks like you need to replace Vo with something. Go back to your schematic and see if you can express Vo in terms of the other quantities pertaining to the branch it's in.

Can I replace Vo with V-10/25 ?

 

[gneill]

Can I replace Vo with V-10/25 ?

Do you mean (V-10)/25? (Order of operations is important). No, that would be the branch current flowing from v towards the 10 V source. But that's a start. What would be Vo in terms of that current?

 

[sammyqw]

Do you mean (V-10)/25? (Order of operations is important). No, that would be the branch current flowing from v towards the 10 V source. But that's a start. What would be Vo in terms of that current?

it would be some current i = Vo/20 ?

 

[gneill]

it would be some current i = Vo/20 ?

That's the idea. But you've already identified the branch current in post #3.

 

[sammyqw]

That's the idea. But you've already identified the branch current in post #3.

Can I do i=10/25 = 0.4A then find Vo= (0.4)20 =8V and then just replace it in my equation 2?

 

[gneill]

Can I do i=10/25 = 0.4A then find Vo= (0.4)20 =8V and then just replace it in my equation 2?

No because the battery voltage is not across the branch. What is an expression for the branch current (you wrote one as a term in your node equation!)?