A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. This kind of machine is impossible, as it would violate either the first or second law of thermodynamics or both. These laws of thermodynamics apply regardless of the size of the system.

Is it possible to build a perpetual motion machine?

The first law of thermodynamics is the law of conservation of energy. It states that energy is always conserved. ... To keep a machine moving, the energy applied should stay with the machine without any losses. Because of this fact alone, it is impossible to build perpetual motion machines.

What are some examples of perpetual motion machines?

Other examples of attempts at a perpetual motion machine include 16th Century windmills, 17th Century siphons, and some water wheel designs. It must be noted that some perpetual motion machines have been designed genuinely in the spirit of curiosity and science.