What does the symbol Eh represent in thermodynamics?

The symbol Eh in thermodynamics specifically represents a change in thermal energy. This quantity indicates the difference in thermal energy of a system as it undergoes a change, such as heating or cooling, and is crucial in understanding energy transfer processes between systems.

In many thermodynamic contexts, the change in thermal energy is associated with various physical processes, including phase changes, heating, and the work done by or on a system. It's important to note that when considering energy transfers in heat engines or refrigerators, understanding the change in thermal energy helps in analyzing the efficiency and performance of these systems.

The other options, while they may relate to energy or thermal concepts, do not accurately define what Eh denotes in thermodynamics. For instance, energy in joules is a broader term that encompasses various forms of energy but does not specifically refer to thermal changes. Specific heat is a property that measures how much energy is required to change the temperature of a substance, but it is not what the symbol Eh signifies directly. Lastly, a change in temperature represents the difference in temperature, which is related but not directly synonymous with changes in thermal energy. Therefore, acknowledging that Eh signifies a change in thermal energy aligns with its role in thermodynamic principles.