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Nice experiment!

But think: why would a current flow in a particular direction and not the other? Is the system somehow asymmetric? As the other answers have suggested, this is probably a thermo-electric current due to the Seebeck effect (a complication I didn't want to get into for your other question).

But now that we're there, here's another thing to try: can you change which direction the current flows by how you are heating the resistor? Does the magnitude or direction of current change when you heat one wire of the resistor versus the other? The Seebeck effect comes into play at electrical interfaces, where there's asymmetry, so the direction of the interface would determine the direction of the current!

The asymmetry issue is another way how you can see that you can't reverse the standard Joule heating: You will get the same heating for a current running either direction through the resistor. But if you cool the resistor to try to undo it, which way would the resulting current flow?

Nice experiment!

But think: why would a current flow in a particular direction and not the other? Is the system somehow asymmetric? As the other answers have suggested, this is probably a thermo-electric current due to the Seebeck effect (a complication I didn't want to get into for your other question).

But now that we're there, here's another thing to try: can you change which direction the current flows by how you are heating the resistor? Does the magnitude or direction of current change when you heat one wire of the resistor versus the other? The Seebeck effect comes into play at electrical interfaces, where there's asymmetry, so the direction of the interface would determine the direction of the current!

Nice experiment!

But think: why would a current flow in a particular direction and not the other? Is the system somehow asymmetric? As the other answers have suggested, this is probably a thermo-electric current due to the Seebeck effect (a complication I didn't want to get into for your other question).

But now that we're there, here's another thing to try: can you change which direction the current flows by how you are heating the resistor? Does the magnitude or direction of current change when you heat one wire of the resistor versus the other? The Seebeck effect comes into play at electrical interfaces, where there's asymmetry, so the direction of the interface would determine the direction of the current!

The asymmetry issue is another way how you can see that you can't reverse the standard Joule heating: You will get the same heating for a current running either direction through the resistor. But if you cool the resistor to try to undo it, which way would the resulting current flow?

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Nice experiment!

But think: why would a current flow in a particular direction and not the other? Is the system somehow asymmetric? As the other answers have suggested, this is probably a thermo-electric current due to the Seebeck effect (a complication I didn't want to get into for your other question).

But now that we're there, here's another thing to try: can you change which direction the current flows by how you are heating the resistor? Does the magnitude or direction of current change when you heat one wire of the resistor versus the other? The Seebeck effect comes into play at electrical interfaces, where there's asymmetry, so the direction of the interface would determine the direction of the current!