Final answer:
A reading of zero when measuring the resistance of a contact coil typically indicates a short circuit, meaning there is no resistance and a direct path for electricity flow.
Step-by-step explanation:
When measuring the resistance of a contact coil, a reading of zero indicates a short circuit. This is because a reading of zero ohms implies that there is a direct path for electricity to flow with no resistance, which characterizes a short circuit. On the contrary, a high resistance would show a non-zero value, an open circuit would prevent any current flow and thus the multimeter would not be able to measure any continuity, resulting in an infinite or undefined resistance reading. An indeterminate reading could represent a fluctuating or uncertain resistance value, which is not the case here. It's important to note that in practical situations, true zero resistance is almost impossible due to the inherent resistance in all materials. However, for most practical purposes, a reading that is very close to zero is interpreted as a short circuit.