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Homework Help: Thevenin equivalent circuit

  1. Jan 5, 2015 #1
    1. The problem statement, all variables and given/known data
    I am to find the thevenin equivalent circuit without the load resistor (to the left of terminals a &b

    2. Relevant equations

    From class notes:
    1- Remove the load resistor
    2- find the open circuit voltage across a & b
    3- Remove all voltage sources (replace with short circuit)
    4- Detrmine the equivalent circuit resistance across the break
    5- Form an equivalent circuit

    3. The attempt at a solution

    I have not come across the symbol that looks like an 8 with the 2amps next to it so far, and i dont understand how this will effect my circuit, is it a voltage source, how will it effect the resistors?
    Without acknowledging it,
    my resistors are all in parralel so Restance total is
    1/RT = 1/R1 + 1/R2 + 1/R3
    1/RT = 1/4 + 1/12 + 1/1
    1/RT = 3/12 + 1/12 + 12/12
    1/RT = 16/12
    RT = 12/16
    RT = 0.75

    32v/0.75 ohms = 42.667 Amps
    Vab = 32 - 1x42.667Amps = -10.667 Volts

    Resistance looking in has already been calulated as 0.75 ohms


    Attached Files:

  2. jcsd
  3. Jan 5, 2015 #2


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    Science Advisor
    Homework Helper
    2017 Award

    Hello Alex, and welcome to PF :)

    The 2A thingy is a (slightly outdated) symbol for a current source.

    I don't see how you can consider all R as parallel.
  4. Jan 5, 2015 #3


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    Staff: Mentor

    Hi Alexander Max, Welcome to Physics Forums.

    As BvU stated, the two-circle symbol represents a current source. It's a bit outmoded as a schematic symbol, but it still crops up fairly often.

    Allow me to amend your algorithm's item 3 a bit, since in its given form it doesn't address current sources:

    3 - Suppress all independent sources: Replace voltage sources with a short circuit and all current sources with an open circuit (simply remove them entirely).
  5. Jan 6, 2015 #4
    Thank you for your help!
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