Finding Unknown quantities in a circuit

In summary, the conversation discusses the use of Kirchhoff's current law to solve for I3 in a circuit problem. The individual arrived at the correct answer of I3 = 0.5A by considering the current through identical resistors and using Ohm's and Kirchoff's Laws. They also mention another approach involving power calculations to find the voltage and resistance values. Ultimately, both methods lead to the same solution.
  • #1
Josh225
51
3

Homework Statement


See attached photo

Homework Equations



Kirchhoff's current law[/B]

The Attempt at a Solution



So, I was solving for I3 and got the correct answer, but I want to be sure that I arrived at the right answer by using a reliable thought process. I don't want to get lucky!

So, I had already determied I1 and got 1A.

With that information I thought... It starts out with 2 A, and there are 2 identical resistors (R2 and R3). I3 = 1 A, so these 2 resistors must each have a current of .5 A going through it. From that I found that I3 = .5A

Is this a reliable thought process? What are some other ways to view this problem?

Thanks!
 

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  • #2
Your method is correct. I believe it is the only way to solve this problem.
 
  • #3
Any solution is going to rely on Ohm's and Kirchoff's Laws.
But you could use the fact that R1 is dissipating 30W to find ##\left(\sf using~\color{blue}{power﹦\frac{E^2}R}\right)## that E=30V

Then, with the battery delivering 30×2=60W, this means the R2 R3 combination is dissipating 30W. So R2##\|##R3 must be 30Ω, and so on ...
 

FAQ: Finding Unknown quantities in a circuit

How do you calculate unknown quantities in a circuit?

To calculate unknown quantities in a circuit, you need to use Ohm's Law, which states that voltage (V) is equal to current (I) multiplied by resistance (R). This equation can be rearranged to solve for any of the three variables, depending on which ones are known and which one is unknown.

What are the most common unknown quantities in a circuit?

The most common unknown quantities in a circuit are voltage, current, and resistance. These are the three fundamental variables that determine the behavior of an electric circuit.

How do you measure voltage, current, and resistance in a circuit?

Voltage is measured using a voltmeter, current is measured using an ammeter, and resistance is measured using an ohmmeter. These tools are commonly found in a multimeter, which can measure all three variables.

Can you use Ohm's Law to solve for unknown quantities in any type of circuit?

Yes, Ohm's Law can be used to solve for unknown quantities in any type of circuit, as long as the circuit is composed of passive components (such as resistors, capacitors, and inductors) and follows the rules of linear circuit analysis.

Are there any other methods besides Ohm's Law to find unknown quantities in a circuit?

Yes, there are other methods such as Kirchhoff's laws and the node-voltage method, which can be used to find unknown quantities in more complex circuits. However, Ohm's Law is the most commonly used method for simple circuits due to its simplicity and accuracy.

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