# Help in Electric Circuit Analysis -- One current source and a resistor network

• Engineering
• Xiao Xiao
In summary: At first I didn't the same as in the second circuit, I used current division on the (1ohm and 2ohm resistors) then got the currents for other branches using the same method, but it was the wrong answer and the correct one was by doing like in the first circuit first, but I don't understand why I was wrong, and why it doesn't work for i1 like it does for the other currents. They're all connected to just two resistors.Edit: okay, wait, forget what is said, so I was wrong, the correct thing to do, using the second circuit in my previous reply, first Req=6 (for the 8||12=4.8 and with
Xiao Xiao
Homework Statement
In the circuit shown, determine Vx and the power absorbed by the 12 ohm resistor.
Relevant Equations
We used Ohm's law and current division.

First we found Vx by making and Req which equals to 6ohm (the circuit will like like a branch with as shown in the second circuit) we find the current in the 4ohm resistor branch using current division.

And to find the power absorbed in 12 ohm resistor we need to find the value of current that passes through that branch (i4), using current dividor as shown in the third circuit. What I don't get is why did we put an Req to find i1, we had only two resistor branches involved, so why couldn't it have worked if we used Req with the 1ohm, but it worked to find the current in other branches (after making an Req for each wire(?)?

Edit: turns out we can't put two pictures or idk, anyway, we found an Req first, so the circuit would look like, the current with ameber branch, the two parallel resistor branches (2ohm and Req=4ohm) and we used that to find Vx.

Then we go back to the original circuit, we make Req=6ohm (using the branch with 4ohm, 3 ohm, 6ohm, resistors). If that helps imagining how it looks.
o9

I'm only seeing one circuit diagram, but it sounds from your description that there are 3 total diagrams?

berkeman said:
I'm only seeing one circuit diagram, but it sounds from your description that there are 3 total diagrams?
Yeah I noticed it didn't work, and tried to describe it with words instead.

It sounded like you had the right approach. Fold up (combine) all the resistors to the right of the Vx resistor, and find Vx. Then start un-folding them back to work your way to finding the voltage and current for the 12 Ohm resistor. Can you post your work on that?

berkeman said:
It sounded like you had the right approach. Fold up (combine) all the resistors to the right of the Vx resistor, and find Vx. Then start un-folding them back to work your way to finding the voltage and current for the 12 Ohm resistor. Can you post your work on that?

berkeman said:
It sounded like you had the right approach. Fold up (combine) all the resistors to the right of the Vx resistor, and find Vx. Then start un-folding them back to work your way to finding the voltage and current for the 12 Ohm resistor. Can you post your work on that?
View attachment 281124
View attachment 281125View attachment 281124
Xiao Xiao said:
At first I didn't the same as in the second circuit, I used current division on the (1ohm and 2ohm resistors) then got the currents for other branches using the same method, but it was the wrong answer and the correct one was by doing like in the first circuit first, but I don't understand why I was wrong, and why it doesn't work for i1 like it does for the other currents. They're all connected to just two resistors.

Edit: okay, wait, forget what is said, so I was wrong, the correct thing to do, using the second circuit in my previous reply, first Req=6 (for the 8||12=4.8 and with 1.2 ohm resister). Then we find i2, after that we unfold it back and find i4? So to use current division there has to be only two resistors that aren't connected to any other branch (the current doesn't get divided after its done going though them)?

Last edited:

## 1. What is an electric circuit?

An electric circuit is a closed loop through which an electric current can flow. It consists of a power source, such as a battery, and various components, such as resistors and capacitors, that are connected in a specific way to control the flow of electricity.

## 2. What is a current source?

A current source is an electronic device that provides a constant flow of electric current in a circuit. It is often represented by a circle with an arrow pointing towards the circuit, indicating the direction of the current flow.

## 3. How do I analyze a circuit with one current source and a resistor network?

To analyze a circuit with one current source and a resistor network, you can use Kirchhoff's laws and Ohm's law. Kirchhoff's laws state that the sum of the currents entering a node in a circuit is equal to the sum of the currents leaving that node. Ohm's law states that the voltage across a resistor is equal to the product of the current flowing through it and its resistance.

## 4. What is the purpose of a resistor in a circuit?

A resistor is used to control the flow of electric current in a circuit. It resists the flow of electricity, which can be useful for regulating the amount of current in a circuit or for converting electrical energy into heat.

## 5. How can I calculate the total resistance in a resistor network?

The total resistance in a resistor network can be calculated by adding the individual resistances in series or using the parallel resistance formula for resistors in parallel. In series, the total resistance is equal to the sum of all the individual resistances. In parallel, the total resistance is equal to the reciprocal of the sum of the reciprocals of each individual resistance.

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