1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Lab Report- Circuits Calculating Resistance and Current

  1. Mar 3, 2015 #1
    I am struggling with doing calculations for a physics lab report. I understand how to calculate the equivalent resistance and the voltage of the battery. I am struggling with calculating the resistance of each resistor and the current of each resistor.

    I am sorry but I am getting very frustrated because I looked in the book and tried to follow the examples, but the book examples were too simplified. They separated series and parallel resistors into two different examples. In my example, there is a circuit with the resistors in parallel and in series. Then, I talked to her again and he said to look in the book again and she won't help me. I am frustrated because she helped other students with it.

    I need to calculate the resistance of each resistor and the current of each resistor. I can only use the resistances of each resistor and the voltage of the battery.

    R1=10.44
    R2=10.36
    R3=10.12
    R4=10.13

    Vbatt=5.85 V

    I attempted to the voltages and currents of each resistor but do not understand about breaking them down into parallel and series. Like for circuit 5, I broke them into series and parallel. Then how do I calculate the current of each resistor? Do I calculate the current, resistance and go back and forth? Also, voltage drops confuse me. I attached the work I have and what I attempted to do.

    If someone could check it over to make sure I do it correctly that would be great and explain the process that would be amazing! It is due very soon and I don't know what to do.
     

    Attached Files:

  2. jcsd
  3. Mar 3, 2015 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    In general, yes.
    In circuit 5, finding the voltage at two resistors can be done without further calculations. That leaves two resistors that are in [...]

    If your scanned work refers to circuit 5, I don't understand what you calculated where. Please write it down here, including explanations what you are doing.
     
  4. Mar 3, 2015 #3
    Scan 7 showed Circuit 5. I broke it down because R3 and R4 were in series as well as R1 and R2. Then R34 and R12 were in parallel. This created R1234. I calculated the equivalent reistance of R1234 first by using the series equation and adding the resistances together. Then I did 1/R1234 to calculate the equivalent resistance. For the battery's current I used the voltage divided by the equivalent resistance.


    Here's where I don't understnad R1, R2, R3 and R4. how do I calculate the restiantces and currents. I12=V12/R12. I got I12=I1=I2

    Then for V1=I1R1. Then I calculated V2 from the current I12xR2. Same with V3. Could someone check my work?

    I need to find all the calculations for Circuits 5-8.
     
  5. Mar 3, 2015 #4

    gneill

    User Avatar

    Staff: Mentor

    It looks to me that you are given the values of the resistances:
    Aren't they the R1, R2,...R4 values above, presumably in Ohms?

    So perhaps you mean that you want to calculate the potential drop (voltage ) across each resistor and the current through each resistor?

    You should have covered the basics of serial and parallel connections and what they imply for voltages and currents. That is, parallel components share the same potential drop but may have different currents, whereas series-connected components all have the same current but may have different potential drops on each component.
     
  6. Mar 3, 2015 #5
    I have to check on this. I'm not sure if it is each resistor's current and resistance or current and voltage. We have the resistances but not sure if we have to compare measured and calculated resistances. I am pretty sure I was mistaken. We need the current and Voltages of each resistor not restances.
     
  7. Mar 4, 2015 #6

    andrevdh

    User Avatar
    Homework Helper

    Your work looks correct.
    I think you are just confused about what you are supposed to do and not how to do it.
    Your physics and calculations are fine.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted