A source behind a series resistance

This is the circuit from the lecture, running. Change it and the answer changes with it:

• Click any component value to edit it, or drag components to rearrange.
• The wrench opens a step-by-step analysis — it chooses a reference node and writes the node equations. Leave its Domain on the DC operating point for this deck.
• The crosshairs probe reads a node voltage or a branch current, so you can check any intermediate result rather than only the final answer.

Probe the load: 8 V and 1 mA. Then open the other form beside it and probe the same two things. They match, which is what "equivalent" means here — and the 4 k in this one carries 1 mA where the other's carries 2 mA, which is what it does not mean.