The second law of thermodynamics forbids a heat engine to have thermal efficiency of what?

greater than Carnot cycle

1 - (Tcold/Thot)

T in KELVIN (dge C + 273)

The second law of thermodynamics states that no heat engine can have a thermal efficiency of 100% or greater.

The second law of thermodynamics states that for any heat engine, the thermal efficiency cannot be equivalent to or greater than 100%. In other words, it is impossible for a heat engine to convert all of the input heat energy into useful work.

To derive this information, one needs to understand the concept of thermal efficiency. The thermal efficiency (η) of a heat engine is defined as the ratio of the useful work output (W) to the heat energy input (QH). Mathematically, it can be expressed as:

η = W / QH

According to the second law of thermodynamics, heat always flows from a higher temperature region to a lower temperature region. This means that in any heat engine, a portion of the input heat energy (QH) will always be dissipated or wasted as heat to the surroundings (QL). Therefore, the useful work output (W) can never equal the total heat energy input (QH).

As a result, the thermal efficiency (η) of a heat engine will always be less than 1, or 100%. In practical terms, it means that there will always be some inefficiency or loss of energy in the process of converting heat into work. The remaining heat energy that is not converted into work is typically released as waste heat.