Formula for Measuring Energy | Energy | Energy Management

The below mentioned article provides a formula for measuring energy.

Energy is the capacity of a physical system to perform work and it is one of the most funda­mental and universal concepts of physical science, but it is remarkably difficult to define in a way that is meaningful to most people. This perhaps reflects the fact that energy is not a “thing” that exists by itself, but is rather an attribute of matter (and also of electromagnetic radiation) that can manifest itself in different ways. It can be observed and measured only indirectly through its effects on matter that acquires, loses, or possesses it.

Basically the energy is of two kinds:

a. Kinetic and

b. Potential.

Kinetic energy is associated with the motion of an object; a body with a mass m and moving at a velocity v possesses the kinetic energy mv²/2. The potential energy is the energy possessed by a body by virtue of its location in a force field— a gravitational, electrical, or magnetic field. For example, when an object of mass m is raised to a height h, its potential energy increases by mgh, where g is a proportionality constant known as the acceleration of gravity.

Energy is measured in terms of its ability to perform work or to transfer heat.

Mechani­cal work is done when a force F displaces an object by a distance d: w = f x d. The basic unit of energy is the Joule. One Joule is the amount of work done when a force of 1 Newton acts over a distance of 1 m; thus 1 J = 1 N-m. The Newton is the amount of force required to ac­celerate a 1-kg mass by 1 m/sec² (1 cal = 4.184 J).

Before dealing with thermodynamics we must be very precise about certain terms. The two most important features of these are system and surroundings. A thermodynamic system is that part of the world, which is under study. Everything that is not a part of the system constitutes the surroundings. The system and surroundings are separated by a boundary.

If our system is one mole of a gas in a container, then the boundary is simply the inner wall of the container itself. The boundary need not be a physical barrier. If matter is not able to pass across the boundary, then the system is said to be closed; otherwise, it is open. A closed sys­tem may still exchange energy with the surroundings unless the system is an isolated one, in which neither matter nor energy can pass across the boundary. The tea in a closed thermos bottle approximates a closed system over a short time interval.

In dealing with thermodynamics, one must be able to unambiguously define the change in the state of a system when it undergoes some process.

This is done by specifying changes in the values of the different state properties using the symbol Δ (delta) as illustrated here for a change in the volume:

∆V = V_final – V_initial