Electrical circuit related problem

[Yammy]

Homework Statement

Determine the value of the voltage Vx
across the 3A current source.

Homework Equations

The Attempt at a Solution

I am really confused about how to do it. What I thought of is to find the voltage across the 4 ohm resistance which is 12 V. I though of subtracting that from the power sources.

But I am not sure which power source should be positive and which one should be negative?
Should I just assume the bigger 6V to be positive just because it is the bigger power source?
I might be completely wrong on this one. So please help me. This is not really a homework problem, this is in one of my practice tests, so I would appreciate any proper explanation I can get, rather than vague hints.
Thank you.

 

[Yammy]

Oh and please look at the attachment for the diagram

 

[gneill]

Homework Statement

Determine the value of the voltage Vx
across the 3A current source.

Homework Equations

The Attempt at a Solution

I am really confused about how to do it. What I thought of is to find the voltage across the 4 ohm resistance which is 12 V. I though of subtracting that from the power sources.

Sure, sounds like a good idea. Use KVL around the left loop.

But I am not sure which power source should be positive and which one should be negative?
Should I just assume the bigger 6V to be positive just because it is the bigger power source?

The voltage sources are labeled with their polarities so no need to guess! Just do a "KVL walk" around the loop in either direction and sum up the potential changes as you go. The math will take care of itself.

 

[Yammy]

ya u r right. Got it and thanks a lot.

 

[rezeew]

Dear student,

Thank you for reaching out for help with this electrical circuit problem. It is important to understand that in order to solve this problem, we need to use Kirchhoff's voltage law (KVL) and Ohm's law.

First, let's label the unknown voltage Vx as a variable, say x. Then, we can write the KVL equation for the loop containing the 3A current source, the 4 ohm resistor, and the two voltage sources as follows:

-6V + x - 12V = 0

Now, let's use Ohm's law to relate the voltage x to the current flowing through the 4 ohm resistor. We know that the current through a resistor is equal to the voltage across it divided by its resistance. Therefore, we can write:

x = (4 ohm)(Ix)

where Ix is the current flowing through the 4 ohm resistor. We can also use Ohm's law to relate the current Ix to the current source of 3A. Since the current source and the resistor are in series, they have the same current flowing through them. Therefore:

Ix = 3A

Now, we can substitute this into our KVL equation to solve for x:

-6V + (4 ohm)(3A) - 12V = 0
-6V + 12V - 12V = 0
x = 6V

Therefore, the voltage across the 3A current source is 6V. We can also verify this by calculating the voltage across the 6V source, which should also be 6V. This means that the positive terminal of the 6V source is connected to the positive terminal of the 3A current source, and the negative terminal of the 6V source is connected to the negative terminal of the 3A current source.

I hope this explanation helps you understand how to approach and solve this type of problem. If you have any further questions, please do not hesitate to ask. Good luck with your studies.

Sincerely,