Final answer:
Power is defined as the rate at which energy is transferred and is often measured in watts. It is a key concept in physics and can apply to both mechanical and electrical systems where energy is converted or work is performed.
Step-by-step explanation:
The rate at which energy is transferred is defined as power. This energy transfer can be due to an external force exerted on an object or system, moving it through a distance, a process which is called work. In electrical systems, power is also described as the rate at which electrical energy is converted into other forms, like thermal energy in a conductor.
For example, when a piston filled with gas is compressed or expanded in a cylinder, work is being done on the gas. The rate at which this energy, whether mechanical or electrical, is transferred into, out of, or within the system is what we call power, typically measured in watts. This concept is a fundamental aspect of thermodynamics and physics in general, evident in situations ranging from fluid dynamics to electrical circuits.