Energy

Energy is a state function commonly defined as the capacity to do work. Since work is defined as the movement of an object through a distance, energy can also be described as the ability to move an object through a distance. As an example, imagine that a bar magnet is placed next to a pile of iron filings (thin slivers of iron metal). The iron filings begin to move toward the iron bar because magnetic energy pulls on the iron filings and causes them to move.

Energy can be a difficult concept to understand. Unlike matter, energy can not be taken hold of or placed on a laboratory bench for study. We know the nature and characteristics of energy best because of the effect it has on objects around it, as in the case of the bar magnet and iron filings mentioned above.

Energy is described in many forms, including mechanical, heat, electrical, magnetic, sound, chemical, and nuclear. Although these forms appear to be very different from each other, they often have much in common and can generally be transformed into one another.

Over time, a number of different units have been used to measure energy. In the British system, for example, the fundamental unit of energy is the foot-pound. One foot-pound is the amount of energy that can move a weight of one pound a distance of one foot. In the metric system, the fundamental unit of energy is the joule (abbreviation: J), named after the English scientist James Prescott Joule (1818-1889). A joule is the amount of energy that can move a weight of one newton a distance of one meter.