Energy

Abstract

Energy is a quantity that not only plays a dominant role in the most diverse areas of the sciences, technology, and economy, but is omnipresent in the everyday world around us. For example, we pay for it with every bill for electricity, gas, and heating oil that arrives at our homes. But we are also confronted more and more with questions about how we can save energy in order to cover our current and future demands. At the beginning of the chapter, the conventional indirect way of defining energy is briefly presented. A much simpler way to introduce this quantity is characterizing it by its typical and easily observable properties using everyday experiences. This phenomenological description may be supported by a direct measuring procedure, a method normally used for the quantification of basic concepts such as length, time, or mass. Subsequently, the law of conservation of energy and different manifestations of energy like that in a stretched spring, a body in motion, etc., are discussed. In this context, important quantities such as pressure and momentum are introduced via the concept of energy.