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    The circuit in question 3 has thevenins being applied to it. My first step was to put r1//r3 as one resistor. I then removed RL. I'm not sure if I include r13 in My r thevenin equation because it is not in an enclosed loop. How would the r thevenin be calculated


    P_20160322_191237 shows my current work with the combined resistor
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    (Original post by A.singh18)
    The circuit in question 3 has thevenins being applied to it. My first step was to put r1//r3 as one resistor. I then removed RL. I'm not sure if I include r13 in My r thevenin equation because it is not in an enclosed loop. How would the r thevenin be calculated


    P_20160322_191237 shows my current work with the combined resistor
    I can't really follow what you've described (it would be much better just to post your working rather than to talk about it) but you need to:

    1. find R_\theta by replacing all current sources with open circuits, and all voltage sources with short circuits, then calculating the resistance as measured across the load terminals of that modified circuit

    2. find V_\theta by analysing the unmodified circuit to compute the voltage across an open circuit load. In this case, you will be computing the voltage due to the current of 1.44 mA through a resistance of 33 || (27 + 12) k ohms.
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    (Original post by atsruser)
    I can't really follow what you've described (it would be much better just to post your working rather than to talk about it) but you need to:

    1. find R_\theta by replacing all current sources with open circuits, and all voltage sources with short circuits, then calculating the resistance as measured across the load terminals of that modified circuit

    2. find V_\theta by analysing the unmodified circuit to compute the voltage across an open circuit load. In this case, you will be computing the voltage due to the current of 1.44 mA through a resistance of 33 || (27 + 12) k ohms.
    (Original post by atsruser)
    I can't really follow what you've described (it would be much better just to post your working rather than to talk about it) but you need to:

    1. find R_\theta by replacing all current sources with open circuits, and all voltage sources with short circuits, then calculating the resistance as measured across the load terminals of that modified circuit

    2. find V_\theta by analysing the unmodified circuit to compute the voltage across an open circuit load. In this case, you will be computing the voltage due to the current of 1.44 mA through a resistance of 33 || (27 + 12) k ohms.
    Thanks for the reply!

    Here is my work for  R_\theta

    And wouldn't the total resistance be (33||12) +27 K ?

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    (Original post by A.singh18)
    Thanks for the reply!

    Here is my work for  R_\theta

    And wouldn't the total resistance be (33||12) +27 K ?
    eh?

    You need to calculate R_{\theta} = (R1 + R2) || R3
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    (Original post by A.singh18)
    Thanks for the reply!

    Here is my work for  R_\theta

    And wouldn't the total resistance be (33||12) +27 K ?
    No. I think that you are allowing the circuit diagram to confuse you as to what is in parallel with what. See uberteknik's answer above.

    Also, I think my description of the calculation of the required voltage may confuse you, if you don't look at the circuit carefully. Across which resistor do you need to calculate the Thevenin voltage?
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    (Original post by uberteknik)
    eh?

    You need to calculate R_{\theta} = (R1 + R2) || R3
    I really don't understand this. The way my diagram is it should be R1+R3 then || R2. Although the diagram I created is probably wrong if that is no the correct way to do this

    (Original post by atsruser)
    No. I think that you are allowing the circuit diagram to confuse you as to what is in parallel with what. See uberteknik's answer above.

    Also, I think my description of the calculation of the required voltage may confuse you, if you don't look at the circuit carefully. Across which resistor do you need to calculate the Thevenin voltage?
    Voltage across R13 altering putting them in parallel
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    (Original post by A.singh18)
    I really don't understand this. The way my diagram is it should be R1+R3 then || R2. Although the diagram I created is probably wrong if that is no the correct way to do this
    No, from your diagram, the Thevenin resistance is as given by uberteknik. If this isn't clear, you probably need to revise serial and parallel resistance calculations.

    Note the locations of the top and bottom ends of R_3 - what are they connected to?

    Voltage across R13..
    I guess you mean R_3 - yes, this is the resistance across which to calculate the Thevenin voltage.

    .. altering putting them in parallel
    This is meaningless, I'm afraid. I'm not sure what you're trying to say here.
 
 
 
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