Which limitation arises when attempting to operate a Carnot heat engine at near-absolute-zero cold reservoir temperature?

💡 Explanation

When the cold reservoir temperature approaches absolute zero in a Carnot engine, the temperature difference decreases, therefore the ideal efficiency (1 - T_cold/T_hot) tends to zero, drastically reducing potential work output. Therefore work output approaches zero, rather than conductivity, tunneling or thermodynamic violation all of which describe other issues.

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