Question

explain why it makes some sense that a large temperature difference enables greater efficiency.

Answer 1

We observe in the laboratory that:

1. For heat to flow from a source to a sink, there must be a temperature difference.
2. When heat is transferred from one body to another, the temperatures equalize. As the temperature of the heat source falls, that of the heat sink rises.
3. When temperatures are equal, no more heat can be transferred, even though the hot and cold objects still contain heat.
4. So, as the temperature difference falls the rate and amout of heat getting transferred decreases which will ultimately decrease the work done.
5. The maximum (or "theoretical") efficiency of any heat engine is described in terms of the temperatures of the heat source and heat sink. Temperatures are expressed in the Kelvin scale (Celsius + 273).           
6.                                 

                              So, we see that as temeperature difference increases, efficiency will increase.