Work and Internal Energy

Previously, the concept of heat was introduced and the First Law of Thermodynamics was represented mathematically. A more accurate version of this law is included in this post. The first law states that the internal energy of a system is equal to the sum of the heat input and the work done on a system (for the work a system does on its surroundings, simply change the sign of the W term in the equation for internal energy).

Work is defined in physics to be a force applied over a distance- in the case of thermodynamics, work is any transfer of energy that is not heat. This reasoning seems to be circular, but bear with the logic as these definitions in terms of one another have practical applications. Everyday examples that involve heat include:

-Adding milk to coffee
-ignition in a car engine (starting the car)

Examples of work:

- Microwaving a meal (NOT heat! More on this later...)
- Inflating a balloon