enter image description here

Can someone give an explanation to why there no current in i0 (or why does i0 equal 0)? It was a step I had to know before using Kirchoff's laws.

Also, is there a voltage across the nodes that i0 goes between?

  • 3
    \$\begingroup\$ There's no return path. The entire lower conductor is one node. \$\endgroup\$
    – Chu
    Mar 2, 2016 at 1:06
  • 1
    \$\begingroup\$ Also, if you remember the current into a node = current out of a node, then you can see that the net current between those two nodes must be zero. \$\endgroup\$
    – Keegan Jay
    Mar 2, 2016 at 1:16
  • \$\begingroup\$ Related: Kirchhoff's Current Law at the ground node? \$\endgroup\$
    – The Photon
    Mar 2, 2016 at 1:36
  • \$\begingroup\$ Specifically, look up the cut-set version of the Kirchoff Current Law. \$\endgroup\$
    – The Photon
    Mar 2, 2016 at 1:38

2 Answers 2


Assuming ideal circuit elements and conductors:

Simply because there is no return path for \$i_o\$.

The entire lower line (call it ground or common) in the schematic is considered to be one node, therefore there is considered to be no voltage difference across it either.

(Suppose that there was a current flowing in \$i_o\$. Then the only way back to the starting point would be trough the same node but in opposite direction, meaning that the sum of the currents is \$i_o + (- i_o) = 0\$.)


This would be like taking a battery and connecting only one terminal of it to your circuit. You need a path for the current to return


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.