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Hopefully the title explains it. As an example, what is the voltage at node one in the schematic below? And more importantly, why? I believe the answer is 0V, but I suppose what I'm thinking is: Why isn't it 125V? Thanks for any help you can give.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Gorlath, you are a champion. It wouldn't let me put it in there because I don't have enough points. \$\endgroup\$ Mar 19, 2013 at 4:24
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    \$\begingroup\$ Voltage relative to what? There can be no answer without a reference to measure in comparison to. It's unclear, but someone may have drawn a variety of ground symbol there, and if that was the intent it would make this the implicit reference point for measuring other voltages, and thus 0 relative to itself. \$\endgroup\$ Mar 19, 2013 at 4:24
  • \$\begingroup\$ @Joseph Rocca Are those 120V AC? \$\endgroup\$ Mar 19, 2013 at 4:51
  • \$\begingroup\$ DC. Thanks guys. All makes so much more sense now :) \$\endgroup\$ Mar 19, 2013 at 6:40

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To say the "voltage at" is incorrect. Voltage is a difference.

When people say the voltage at a point, what they really mean is the voltage from said point to ground.

Because there is a ground symbol next to your node with nothing in between you can say that the voltage from the node to ground is zero.

see http://en.wikipedia.org/wiki/Voltage

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  • \$\begingroup\$ Ahh! Thanks so much. So for the node underneath the bottom voltage source: is that node at a voltage of -125V relative to ground? \$\endgroup\$ Mar 19, 2013 at 5:19
  • \$\begingroup\$ @JosephRocca, Yep! \$\endgroup\$
    – Mark B
    Mar 19, 2013 at 5:30
  • \$\begingroup\$ Brilliant! It's all starting to make sense. Thanks. \$\endgroup\$ Mar 19, 2013 at 6:41

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