I have been trying to solve this circuit with about every method I could think of: node voltage, mesh current, branch current, superposition, and source simplification. Although using one of these methods always worked for circuits with no dependent sources and all voltage or current sources, in this case I obtain a different solution with each method. So I assume, there must be something wrong with the assumptions I used when setting the circuit equations. The solution should be: \( I = -12 (A) \)

Question 1 - Node voltage method (NVL) :

So what is correct, i.e. can we assume that the current in the left branch is constant 2A:

a) \( \frac{V_a}{3} = 2 \), or

b) \( 2 + \frac{V_a - 4}{2} + \frac{V_a - 3V_r}{5} = 0 \) , or

c) \( \frac{V_a}{3}+ \frac{V_a - 4}{2} + \frac{V_a - 3V_r}{5} = 0 \) , or

d) \( 2 + \frac{V_a}{3} + \frac{V_a - 4}{2} + \frac{V_a - 3V_r}{5} = 0 \)

Question 2 - Superposition:

At first the 2A source is suppressed resulting in the following circuit:

\( -3V_r + 5I + 4 + 2I = 0 \)

\( V_r = 2I \)

\( I = -4 (A) \)

Then the 4V independent voltage source is suppressed resulting in the following circuit:

By the branch current method:

\( I = -2.4 (A) \)

So, by superposition the total current should be:

\( I = -6.4 (A) \),

which differs from the solution in the book. What is the correct way to solve this?