Find the Thevenin's Equivalent for the following circuits

[AlphaLibrae]

Homework Statement

3) Find the Thevenin equivalent of the following circuit: i.e. find the thevenin's voltage and thevenin's resistance

4)Find the Thevenin's voltage and Thevenin's resistance for the following circuit and hence find the current through the load resistor

The problems and the circuit diagrams are here:

Relevant Equations

Kirchhoff's Laws
The current entering any junction is equal to the current leaving that junction. i2 + i3 = i1 + i4

The directed sum of the potential differences (voltages) around any closed loop is zero.
v1 + v2 + v3 +v4 = 0

I have actually already written out and solved for my own solutions to these problems, but I was wondering if I could get a second opinion on my solutions:

For Problem 3:
For Problem 4:

 

[gneill]

In future, please post each problem in separate posts. This is PF policy. We find that this avoids "crosstalk" confusion when multiple people are engaged with different problems in the same thread.

For your first problem the Thevenin resistance looks okay but the Thevenin voltage does not. I think you've dropped a sign when solving for $i_2$.

 

[AlphaLibrae]

In future, please post each problem in separate posts. This is PF policy. We find that this avoids "crosstalk" confusion when multiple people are engaged with different problems in the same thread.

For your first problem the Thevenin resistance looks okay but the Thevenin voltage does not. I think you've dropped a sign when solving for $i_2$.

Ah ok, so would it actually be 15 + (6)(0.83 = 19.98 V?

 

[gneill]

Ah ok, so would it actually be 15 + (6)(0.83 = 19.98 V?

Yes. With a few more digits used for intermediate values you'd find out that it comes out to 20.0 V.

 

[fresh_42]

In future, please post each problem in separate posts.

... and please upload photos instead of link to another provider, because otherwise it happens what just [2/22/20 - 1426 GMT] happened: "imgur refuses to connect" or the link will be broken long term!

 

[epenguin]

... and please upload photos instead of link to another provider, because otherwise it happens what just [2/22/20 - 1426 GMT] happened: "imgur refuses to connect" or the link will be broken long term!

Can't see a thin.