Ohmmeter test on an inductor: An ohmmeter is placed across a coil and the pointer indicates approximately 0 Ω. What condition does this imply about the inductor?

Introduction / Context:
Basic troubleshooting of inductors and transformer windings often starts with a simple resistance test. While inductors have low DC resistance, they should not read a true short (zero ohms). Interpreting ohmmeter readings correctly helps rapidly identify faults without specialized equipment.

Given Data / Assumptions:

• Ohmmeter across a coil indicates ~0 Ω.
• We consider a typical small to medium coil with finite winding resistance.
• No other parallel paths are connected during the test.

Concept / Approach:
A healthy coil exhibits a small but non-zero DC resistance due to copper wire length. A reading of near 0 Ω indicates the winding is shorted (e.g., turns shorted together or terminals shorted), bypassing the normal length of wire and reducing measured resistance to nearly zero.

Step-by-Step Solution:

Verification / Alternative check:
Compare with “open” failure: an open winding reads infinite resistance. A “partly shorted” winding typically shows lower-than-normal but not zero resistance; performance under AC will also change (higher losses, overheating).

Why Other Options Are Wrong:

• Open: Would read very high/infinite resistance, not zero.
• Good: A good coil should not read exactly zero; some resistance is expected.
• Partly shorted: Would not usually be exactly 0 Ω; meter reads small but non-zero.

Common Pitfalls:

• Interpreting “very low” as “healthy”; check datasheet expected DCR values.

Final Answer:
shorted