Circuit Theory Problem: Find Vx for 5A Source to Supply 60W

In summary, the problem is finding the value of Vx in the circuit below such that the power supplied by the 5-A source is 60W. To do this, you could use superposition to figure out what value Vx is across the 4Ohm resistor, or you could use KVL or KCL to find the voltage and current for every element below the 3A current source.
  • #1
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Hey,

I'm having a bit of difficulty with this specific circuit theory problem... We understand the basics, Ohm's law, Kirchoff's voltage and current laws, voltage and current division... I'm just confused about what to do with this problem:

Find the value of Vx in the circuit below such that the power supplied by the 5-A source is 60W.

http://synthdriven.com/images/deletable/EEN201-03.jpg

I mean, I figure I'd start with the 5A current source... P=IV, so the potential over that current source would be 12v? I don't know, I'm really confused. The shape of this thing has me confused as well, what's in parallel with what and what's in series?

I'm completely stumped. Any pointers on how to go about this problem?
 
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  • #2
You didn't mentioned superposition, so I'll assume that it is part of the course too.

You could try to use superposition (of the 4 sources) to work out to the 12V across the 5A source. From there, it should be possible to know what value Vx is.
 
  • #3
haven't been introduced to superposition yet...
 
  • #4
In which case, is it possible that you learn about the method and apply it on the problem? Here is a good place to start:
http://www.allaboutcircuits.com/vol_1/chpt_10/6.html"

You could, of course, use something in the like of KVL or KCL to solve the problem, but I don't think it will be any easier than superposition.
 
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  • #5
we haven't learned superposition yet, this is an exercise to teach us how to use KCL KVL current division, voltage division and ohm's law to find values

i just don't know how to start this problem using KCL KCL current division, voltage division and ohm's law... not superposition... I'm confused with where to start
 
  • #6
If the picture is confusing you, begin by redrawing it with all of the shorts gone, so the element ends touch each other and there are no straight segments of wire connecting nodes.

If you do that you should get a triangle at the bottom because everything at the bottom is touching so you can pinch that together to one node. Then since you have a voltage source on the left and you figued out V through the 5 amp source, you can use KVL to find the voltage drop across the 4Ohm resistor. Now you should know the voltage and current for every element below the 3A current source, and I won't spoil the rest for you but do similarly to the remaining pieces and you should be able to find Vx easily.
 

FAQ: Circuit Theory Problem: Find Vx for 5A Source to Supply 60W

1. What is Circuit Theory?

Circuit theory is a branch of electrical engineering that deals with the analysis and design of electrical circuits. It involves understanding the behavior of currents and voltages in various components of a circuit, such as resistors, capacitors, and inductors, and how they affect the overall functioning of the circuit.

2. How is Vx calculated in this problem?

In order to calculate Vx, we can use Ohm's law, which states that the voltage (V) across a resistor is equal to the current (I) flowing through it multiplied by its resistance (R). In this circuit, Vx is the voltage across the resistor, which can be calculated by multiplying the current of the 5A source by the resistance of the circuit, which is 12 ohms. Therefore, Vx = 5A x 12 ohms = 60V.

3. What is the significance of the 5A source and 60W supply in this problem?

The 5A source represents the current flowing through the circuit, while the 60W supply represents the power being supplied to the circuit. In this problem, we are given the power (60W) and we need to find the voltage (Vx) using the given current (5A) and resistance (12 ohms) values.

4. Can Vx be found using other methods besides Ohm's law?

Yes, Vx can also be found using Kirchhoff's laws, which are fundamental principles in circuit theory. Kirchhoff's voltage law states that the sum of all voltages in a closed loop must equal zero, while Kirchhoff's current law states that the sum of all currents entering and leaving a node must also equal zero. By applying these laws, we can solve for Vx in this circuit.

5. How is this problem applicable in real-life situations?

Problems like this one can be commonly found in the design and analysis of electrical circuits, which are used in a wide range of devices and systems such as power grids, electronic circuits, and communication systems. By understanding and applying circuit theory, engineers and scientists are able to design and optimize these systems for various applications.

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