Thermocouple question.

I did an experiment where I had to measure the temperature of a vessel using thermocouples.


With the basic circuit, I got an EMF value of -0.04 mV. I then added an extension cable to see what effect it had and I got an EMF value of -0.08 mV.


If length is proportional to resistance which is proportional to voltage, shouldn't the voltage have increased with the addition of the extension cable? Are my results wrong or is this explained somehow?

Is your Hypothesis correct, yes. Is your data correct, also yes. Your problem is your understanding in the term Voltage. The Voltage or Potential Difference, is the difference in Voltage between the two points. Your first gave 0.04 and your second gave 0.08. Now, even though they we negative, the difference has increased (though negatively). It might be easiest for you to see that when negative they clearly increased. You just have to think, the two voltages increased in their negative size. This literally just comes from Voltage being the difference in two points. It's like the difference between -2 and -4 compared to -2 and -8. The difference is -2 in the first but -6 in the second, yet we still say the difference between -2 and -8 is larger than -2 and -4.

I hope that helped and if you're still confused, please feel free to ask