Simple circuit analysis w/ voltage sources - MasteringPhysics wrong?

In summary, the conversation discusses a simple circuit with 4 resistors, a known voltage source, and an unknown voltage source. The person asking for help has found the voltage drop over one resistor and used it to find the current through another resistor in parallel, giving them the total current through the circuit. They have also tested their answer against MasteringPhysics and found it to be incorrect. However, another person has pointed out that the bottom resistor is actually 1.0Ω instead of 1kΩ, which may be the source of their problem.
  • #1
resigned
6
0

Homework Statement


We are given a simple circuit with 4 resistors, a known voltage source, and an unknown voltage source. The photo is below in my solution attempt.

Homework Equations


V=IR, R(parallel)=(1/R1+1/R2)^-1

The Attempt at a Solution


I found the voltage drop over the given resistor, then used that voltage to find the current through the other resistor in parallel, which gave me the total current through the circuit.

http://imgur.com/HtJootR

My problem is I am pretty sure MasteringPhysics is wrong here. I included all of my work finding my answer, and then tested their answer to show that it is wrong. I am confident in my work but was hoping you could look it over before I go make a dodo of myself to my instructor.
 
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  • #2


resigned said:

Homework Statement


We are given a simple circuit with 4 resistors, a known voltage source, and an unknown voltage source. The photo is below in my solution attempt.


Homework Equations


V=IR, R(parallel)=(1/R1+1/R2)^-1


The Attempt at a Solution


I found the voltage drop over the given resistor, then used that voltage to find the current through the other resistor in parallel, which gave me the total current through the circuit.

http://imgur.com/HtJootR

My problem is I am pretty sure MasteringPhysics is wrong here. I included all of my work finding my answer, and then tested their answer to show that it is wrong. I am confident in my work but was hoping you could look it over before I go make a dodo of myself to my instructor.

Their answers look fine to me.

Write out the voltage drops across each resistor. You know that they will potential drops in the direction of current flow, and that current flow can be either clockwise or counterclockwise. Perform a "KVL walk" around the loop assuming that the current flows in one direction and solve for the required Vba. Then do the same again assuming the current is flowing in the other direction.

By the way, that's a 1.0Ω resistor on the bottom, not a 1kΩ resistor.
 
  • #3


gneill said:
By the way, that's a 1.0Ω resistor on the bottom, not a 1kΩ resistor.

Consarn it. I think that's the source of my problems. I didn't notice it had different units to the rest of them.
 

1. Why is my MasteringPhysics answer for simple circuit analysis with voltage sources wrong?

There could be a few reasons for this. It's possible that you made a mistake in your calculations or in setting up the circuit. It's also possible that there is an error in the problem or in the MasteringPhysics system itself. Double check your work and if you still believe your answer is correct, reach out to your instructor for assistance.

2. How can I improve my understanding of simple circuit analysis with voltage sources?

The best way to improve your understanding is through practice. Make sure you fully understand the concepts and equations involved, and then try solving a variety of problems. You can also seek out additional resources such as textbooks, online tutorials, or asking your instructor for clarification.

3. Can I use any method to solve simple circuit analysis problems with voltage sources?

Yes, there are multiple methods that can be used to solve these types of problems, such as Kirchhoff's laws, Ohm's law, or nodal analysis. It's important to choose the method that works best for the specific problem and to consistently use the same method throughout for accurate results.

4. Why is it important to understand simple circuit analysis with voltage sources?

Simple circuit analysis with voltage sources is a fundamental concept in electrical engineering and is necessary for designing and analyzing more complex circuits. It also has real-life applications in fields such as electronics, power systems, and telecommunications.

5. How can I check my answers for simple circuit analysis with voltage sources?

You can check your answers by using a circuit simulator software, such as SPICE or LTspice, to simulate the circuit and compare the results to your calculations. You can also use an online calculator specifically designed for simple circuit analysis. Additionally, asking for feedback from your instructor or peers can help identify any errors or misunderstandings.

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