Question 14 CEL02 - Chief Engineer - Limited (Alt)

The Correct Answer is C. ### Explanation for Option C ("OL ohms") When a digital multimeter (DMM) is set up to measure resistance (Ohms, as implied by the contactor coil test illustrated in figure "A") and connected across a component that is **open-circuited**, the meter encounters infinite resistance. The DMM cannot complete the internal circuit used for resistance measurement because the path through the coil is broken. On most modern digital multimeters, when the resistance is greater than the meter's maximum range (i.e., infinite resistance), the display reads **OL** (Over Limit or Overload). Since the contactor coil is open-circuited (a complete break in the wire), the resistance is infinite, resulting in the display showing "OL ohms." ### Explanation for Incorrect Options * **A) 0.03 ohms:** This reading indicates a very low resistance, often suggesting a short circuit or a correctly functioning wire/connection with negligible resistance. A healthy contactor coil typically has a measurable, non-zero resistance (e.g., 20–100 ohms). An open circuit always presents infinite resistance, not near-zero resistance. * **B) 22 ohms:** This reading indicates a specific, finite resistance. While 22 ohms might be the typical, healthy resistance of that particular AC contactor coil, it is the reading expected for a **good coil**, not an open-circuited (failed) coil. * **D) 110 V:** This reading indicates a measurement of **voltage** (Volts, V), not resistance (Ohms). For a resistance test (like the one shown in Figure A), the meter must be set to the Ohms function, and the reading will be in units of Ohms (or OL if open). It is impossible to read voltage when the meter is actively measuring resistance.