G azərbaycan respublikasi təHSİl naziRLİYİ azərbaycan texniKİ universiteti M. M. QƏNDİLova e. Q. İsmayilova

Potential Energy
An object possesses potential energy by virtue of its position or condition. The energy of a raised weight, coiled spring, or of an iron bar held near a magnet are examples of potential energy. When the raised weight descends, the wound spring uncoils, or the bar moves toward the magnet, potential energy is expended through motion. The release of this energy can be controlled so the weight, spring, or iron bar can be made to perform useful work as its energy is released.

Kinetic Energy
Kinetic energy is the capacity of an object to do work by virtue of its motion. The greater the speed of an object in motion, the more energy it will expend on impact with another object; thus kinetic energy is a function of the object’s mass times its velocity (KE=1/2 mass × velocity²). A car in motion, an arrow in flight, a pitched baseball, are all examples of kinetic energy. If any of these objects in motion encounters another object, it can expend its kinetic energy in a great deal of work, depending on the mass and velocity of the moving object.
Power
A powerful engine can work faster and turn out more foot-pounds or joules of work per minute than a weak one. However, by working a longer time, the weaker engine can turn out the same amount of work as the strong engine. The amount of work each does is the same, but the rate of work is different. This rate of doing work, measured in work done per unit of time, is called power. As an equation it is expressed as power= work / time

Power is also expressed as horsepower (hp), which became a term of measurement when steam engines were first used to pump water from mines, replacing horses, which had done this work earlier. James Watt, seeking some method of comparing the work of an engine to the work of a horse, found that a strong draft horse working for short periods would average about 33,000 foot-pounds of work per minute or 555-foot pounds per second. He called this rate of doing work the horsepower, and this unit of power has been used ever since.

Energy and power are terms that are often used interchangeably, as though they mean the same thing. Nevertheless, a careful distinction must be made between them: energy is measured in units of work, but power is measured in units of work per unit of time. In practically all cases where work is done, both the amount of work done and the rate at which it is done are important.

The unit for measuring electrical power is the watt. In DC circuits, it is a simple matter to calculate the electrical power by multiplying the voltage by the current (W=E×I). The watt is used to measure the work that any electrical device can do. One example is the ordinary incandescent bulb, always rated in watts. A 100-watt bulb will give more light than a 50-watt bulb because more electrical work is being done in the filament of the larger bulb, and as a result, more heat and light are produced.