physics//thermodynamics

Thermodynamics is the branch of physics that relates heat, work and energy, and in engineering it sets the limits on what any machine that converts energy can achieve, whatever its design. Its laws are statements about all possible machines at once, which is why they can rule out a design without examining it.

Thermodynamics is the branch of physics that relates heat, work and energy, and in engineering it sets the limits on what any machine that converts energy can achieve, whatever its design. Its laws are statements about all possible machines at once, which is why they can rule out a design without examining it.

The first law is conservation: energy changes form but is never created or destroyed, so a machine cannot deliver more work than the energy it takes in.

The second law says that the entropy of an isolated system never decreases. Its consequences are the useful ones: heat flows from hot to cold on its own, no engine can turn all its heat into work (the Carnot efficiency), and erasing information costs a minimum of heat (Landauer's principle).

Every real device loses some energy as heat, and Joule heating in a wire is the everyday case.