Question

What is the sign convention for energy required and released?

Answer 1

Throughout the Thermodynamics Tutorial you will be shown and taught a method for working thermodynamics problems. Following this method closely will increase your chances of successfully solving the problem, especially in the beginning when the terms, concepts, and calculations may be unfamiliar to you.

The first two steps to follow in solving a thermodynamics problem are:

1. Define the system and the surroundings. The system is some object or collection of objects that the problem focuses on, usually one that acts most or causes the most change in the problem, while the surroundings are anything else capable of interacting with (exchanging energy with) the system.

2. Identify and assign signs (positive or negative) to all the kinds of energy and work that enter or leave the system.

In a complicated problem, you may have to repeat these steps more than once, but for now you should only have to do .

Answer 2

A sign convention is required for heat and work energy transfers, and the classical sign convention is selected for these notes. According to the classical sign convention, heat transfer to a system and work done by a system are positive; heat transfer from a system and work done on a system are negative