Probably a very basic question but I have no idea why this happens.
I have a 1K potentiometer. When I measure the resistance over its legs when it is not connected to anything, the results are as expected and alter expectedly when I move the knob.
However, when I connect the pot to a 9V battery and try to measure the pot's resistance, I don't get any readings.
What is the reason for this behavior?
Answer
Because your multimeter can't measure resistance. So it applies a known current, measures the resulting voltage, and computes the resistance from that. 1
So when you're applying an external current to the potentiometer you are upsetting the meter's procedure, and the resulting voltage is probably outside the measurement range.
1 Unless it's really old. In which case it applies a fixed voltage, measures the current, and lets you read the resistance off an inverse scale.
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