When checking a fuse with an ohmmeter (out of circuit), what resistance reading best indicates that the fuse is intact and functioning correctly?
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Azero ohms resistance
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Ba medium resistance
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Ca high resistance
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Dan infinite resistance
Answer
Correct Answer: zero ohms resistance
Explanation
Introduction / Context:A fuse is a protective device intended to open (break) a circuit when excessive current flows. Verifying a fuse with an ohmmeter is a quick diagnostic step during troubleshooting of power and control circuits.
Given Data / Assumptions:
- Fuse removed from the circuit for accurate measurement.
- Digital multimeter set to resistance or continuity mode.
- Room-temperature test with no current flowing.
Concept / Approach:An intact fuse is essentially a short piece of low-resistance metal designed to melt under overcurrent. Therefore, a good fuse should show very low resistance (near zero) and typically will beep in continuity mode. A blown fuse has a melted link and will read infinite or over-range resistance.
Step-by-Step Solution:Remove fuse from the circuit to avoid parallel paths.Place meter leads on both ends of the fuse.Reading near 0 Ω (often a fraction of an ohm) indicates continuity → good fuse.Reading OL or very high resistance indicates an open → blown fuse.
Verification / Alternative check:Visual inspection can reveal a broken element or discoloration, but some fuses fail invisibly; the ohmmeter provides definitive electrical confirmation.
Why Other Options Are Wrong:
- Medium or high resistance: A fuse is not a resistor; such readings indicate a problem or a measurement error.
- Infinite resistance: That is the hallmark of a blown fuse.
Common Pitfalls:
- Measuring in-circuit leads to false continuity through alternate paths.
- Confusing continuity beeper thresholds with absolute resistance; meters typically beep below a few ohms which is normal for a good fuse.
Final Answer:zero ohms resistance