So I'm looking at the circuit below and a little confused by it.

Opposing Ideal Current Sources

How are there two current sources facing opposite directions? What does this even mean and how can it be a valid circuit, since current can only travel one direction?


1 Answer 1


\$v_x\$ can be negative, and in fact it is. Even if it wasn't, \$\alpha\$ could be negative.

Regardless of the fact the question is answerable, it's a nonsense question and applies to no situation I can imagine in real-world engineering. I suggest you give your instructor the answer they want and the forget you ever saw this question.

  • \$\begingroup\$ So am I supposed to understand from the diagram that, even if the ideal current source shows as pointing in a current direction, it doesn't necessarily flow in that direction? \$\endgroup\$
    – PoGaMi
    Oct 3, 2015 at 23:13
  • 1
    \$\begingroup\$ That is correct. The current will flow in the direction determined by the sign of the current value and the direction of the arrow. If the current value is negative, then the current will flow in the opposite direction of the arrow. If the current value is positive, then it will flow in the direction of the arrow. In this example, the current value is negative because the current must flow in the same direction of the fixed current source for the circuit to be valid. \$\endgroup\$
    – Barry
    Oct 3, 2015 at 23:19

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