Final answer:
A 0 ohm reading on a compressor's run winding typically indicates a fault, as windings should have some measurable resistance. Very low resistance requires special methods for measurement, and a 0 ohm reading could inaccurately suggest a short circuit when tested with a standard ohmmeter. For a poorly performing refrigerator connected via a long extension cord, the issue might be voltage drop due to cord resistance.
Step-by-step explanation:
If the run winding on a compressor has a reported resistance of 0 ohms, this is usually indicative of a fault, since windings should have some resistance. However, a true resistance reading of precisely 0 ohms is practically impossible because even the most efficient conductors have some resistance, although it could be very low (less than 0.01 ohms).
Techniques like the four-point method, are used to measure very small resistances because the typical ohmmeter is not sufficiently accurate for such measurements and may mistake a very low resistance for a short circuit. It is important to note that a reading of 0 ohms could indicate a short circuit rather than superconductivity in everyday electrical appliances.
For the case of a refrigerator not running properly with the use of a long, inexpensive extension cord, the problem could be voltage drop due to the resistance of the extension cord. This can cause the refrigerator to receive insufficient power, leading to performance issues.