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MATLAB: Verification of Superposition Principle

  1. Mar 7, 2018 #1
    1. The problem statement, all variables and given/known data

    Verify Superposition Principle using Matlab, given a DC source of 100V, an AC source of 50V, 60Hz and three resistances, R1=10 ohms, R2=20 ohms and R3=15 ohms.

    I created the circuit below and ran the program. Result:


    2. Relevant equations

    None, just running the program.

    3. The attempt at a solution

    Now, the Principle of Superposition states the total current in any part of a linear circuit equals the algebraic sum of the currents produced by each source separately. I am trying to verify the current flowing through R3 = 15 ohms resistance.

    1. I short circuit the DC voltage source and run the program. Result:


    2. I then short circuit the AC voltage source and run the program. Result:


      As clearly can be seen, the Superposition Principle is not verified. I am unable to reason where the discrepancy is.
    Last edited: Mar 7, 2018
  2. jcsd
  3. Mar 7, 2018 #2


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    Staff: Mentor

    I'm not the best with circuits, but I don't understand your result when you short-circuit the DC source. How can you measure 94.4 V in that circuit?
  4. Mar 7, 2018 #3
    Yeah, I altered the step-size to get the accurate value of RMS voltage. Edited the question.
  5. Mar 7, 2018 #4


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    Homework Helper
    Gold Member

    The Current Measurement block is processing a current waveform with both AC and DC components. The block outputs the instantaneous current Not sure how this block will represent a static value of an AC current. What happens if you use an RMS block right before Display3?
  6. Mar 8, 2018 #5

    Sorry for the delayed replies, I am in college for 12-14 hours during the day.
  7. Mar 8, 2018 #6


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    Homework Helper
    Gold Member

    So what is now displayed is the RMS value of the combined AC and DC currents. You should be able to verify this result by using your single-source results and a googleable formula for determining the RMS value of an AC signal with a DC offset.
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