In a 24VDC relay circuit, what effect does increased ambient temperature have on coil current and actuation?

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Multiple Choice

In a 24VDC relay circuit, what effect does increased ambient temperature have on coil current and actuation?

When ambient temperature goes up, the coil’s resistance increases. A relay coil is essentially a resistor powered by a fixed voltage, so the current through it follows I = V/R. With a higher resistance at elevated temperature, the coil current drops. If that current falls below the pull-in (actuation) current the coil needs to generate enough magnetic force to move the contacts, the relay may fail to energize properly. So increased temperature reduces coil current and can prevent proper actuation. The other statements don’t fit: temperature does not reliably increase current, the coil’s performance is affected by temperature, and “brighter” is unrelated to coil actuation.

When ambient temperature goes up, the coil’s resistance increases. A relay coil is essentially a resistor powered by a fixed voltage, so the current through it follows I = V/R. With a higher resistance at elevated temperature, the coil current drops. If that current falls below the pull-in (actuation) current the coil needs to generate enough magnetic force to move the contacts, the relay may fail to energize properly. So increased temperature reduces coil current and can prevent proper actuation. The other statements don’t fit: temperature does not reliably increase current, the coil’s performance is affected by temperature, and “brighter” is unrelated to coil actuation.

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