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e circuit

Can we apply Kirchhoff's volatge law in this simple circuit and say V1=-r1I1 and V2=r2I2 or is there an other connection between voltages and currents?

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    \$\begingroup\$ It all depends on what those circles represent. \$\endgroup\$
    – Andy aka
    Commented Jun 19, 2020 at 13:27
  • \$\begingroup\$ @Andyaka Thanks for the answer sir!They are voltage sources. \$\endgroup\$ Commented Jun 19, 2020 at 13:30
  • \$\begingroup\$ @user287001 Woah dude you are scaring me please stop it \$\endgroup\$ Commented Jun 19, 2020 at 21:50
  • \$\begingroup\$ I can well remove the comment but that doesn't create any solutions. Removed. \$\endgroup\$
    – user136077
    Commented Jun 19, 2020 at 21:52
  • \$\begingroup\$ Homework needs an attempt at a solution \$\endgroup\$
    – Voltage Spike
    Commented Jun 26, 2020 at 19:23

3 Answers 3

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Kirchhoff's Laws are not needed here. If you have an ideal voltage source, and the source value is given (whether a literal value or a function of other circuit values) then you can state the voltage across that source by inspection.

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  • \$\begingroup\$ So could we say V1=-I1r1? \$\endgroup\$ Commented Jun 19, 2020 at 13:39
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    \$\begingroup\$ The polarity of V1 is defined with a direction that is opposite of the defined polarity of the source on the left. \$\endgroup\$ Commented Jun 19, 2020 at 13:47
  • \$\begingroup\$ How could you relate V1 to V2 then? \$\endgroup\$ Commented Jun 19, 2020 at 14:54
  • \$\begingroup\$ There is no relationship between the values of V1 and V2 as they are drawn in this diagram. They are independent voltages. \$\endgroup\$ Commented Jun 19, 2020 at 15:12
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Yes. Kirchoff’s voltage law is a law and can always be applied around a loop in a circuit. If you’ve defined your polarities correctly KVL will give you a correct answer

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  • \$\begingroup\$ And is the correct answer the one i suggested? \$\endgroup\$ Commented Jun 19, 2020 at 13:32
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Judging from their drawing, OP is studying two-port networks.

enter image description here

That said, OP's task may be to find impendence, admittance, or hybrid parameters, and r_1, r_2 are not given values, but the values to be calculated. If so, and if the sources are independent, Ohm's law is sufficient for solving this simple problem: $$ z_{11} = {-V_1 \over I_1}\\ z_{22} = {V_2 \over I_2}\\ z_{12} = z_{21} = 0\\ (r_1=z_{11}; r_2=z_{22}) $$

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