Hi guys can someone please help me with the following problem: Problem

I have figured out the Rth by turning the current sources to open and voltage sources to closed loop and i got this to be 50ohm but not sure how to do the Vth. Thanks

  • 1
    \$\begingroup\$ Sounds like homework, what do you lecture notes tell you about finding Vth? \$\endgroup\$
    – Tyler
    Nov 10, 2015 at 2:46
  • \$\begingroup\$ Turn the current source into a voltage source (considering the two resistors across it) then recalculate. \$\endgroup\$
    – Nedd
    Nov 10, 2015 at 2:49
  • \$\begingroup\$ Just because it looks to be copied right out of a text book should it automatically be considered home work? (He may not even be at home....) \$\endgroup\$
    – Nedd
    Nov 10, 2015 at 2:56
  • \$\begingroup\$ um btw this is from past exam and we are not provided answers :(. This is what i have come up with so far: No current will flow through either the 4ohm or the 6ohm resistor. Therefore would i jst take the voltage drop across the 40ohm and also add the voltage drop across the 260ohm \$\endgroup\$
    – Nadun
    Nov 10, 2015 at 3:26

1 Answer 1


For RTH, you have 4 + (520 V bypasses 260 ==>0) + 40 (current source in series with R is identical to a current source ==>0) + 6 = 50 ohm.

For VTH, measure the open circuit voltage. The 1 A flows through the 40 ohm, generating -40 V. The 520 adds, giving 520-40 = 480 V.


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