Potential energy is the stored energy of position. It can be thought of as energy that is "stored" by any physical system. It is called potential because, in its current form, it is not doing any work or causing any change in its surroundings. It does, however, have the potential to be converted to different forms of energy, such as kinetic energy. The standard unit for measuring such energy is the joule.
One way of explaining energy is that it always falls into one of two forms: potential and kinetic. Some scientists object to this explanation as too simplified or artificial, but it is useful for explaining some general principles. Kinetic energy is that related to movement. Potential energy is that stored within a stationary object.
When an object is displaced from its original position and there is energy pulling it back to that position, potential energy tends to exist. A ball at the end of a spring, for example, has energy that will be converted to kinetic energy when allowed to return to its original position. A weight held above the ground will, when released, have potential energy as gravity pulls it back to its original position.
One of the major principles of this type of energy is the law of conservation of energy, which states that energy can neither be created nor destroyed. The energy expended to lift an object or compress a spring does not simply disappear, it is "stored" as potential energy. It is then released as kinetic energy by a restoring force. The energy input equals the energy output; there is no gain or loss in overall energy.
Types of Potential Energy
There are many different types of potential energy. Potential energy examples include those to do with gravity, elasticity, chemistry, electricity and thermal energy.
Potential elastic energy exists when an elastic object, such as a bow or rubber band, is stretched or otherwise deformed under stress. This can be illustrated by drawing back a bow. Because the shape of the string of the bow is temporarily deformed, when it is released it will attempt to return to its original shape, thus producing the energy which propels the arrow. Until the bow is released, this energy exists as elastic potential energy.
Potential chemical energy is related to the chemical bonds in a molecule. In chemical reactions, chemical potential energy is transformed to other forms of energy as the bonds are broken and reformed. This energy is then released and transformed when the substance is involved in a chemical reaction. For example, when a fuel is burned, its chemical potential energy is converted to heat.
Potential electrical energy takes three primary forms: electrostatic, electrodynamic, and nuclear. An electrically charged object at rest has potential energy which relates to other nearby objects which are also electrically charged. A variation of this is for charged objects which aren't at rest; in this situation there is magnetic potential energy.
Potential electrostatic energy exists when a charged particle is at rest. It has potential energy because of its position in relation to other charged particles. Potential electrodynamic energy exists because of moving charged particles. These particles can form an electromagnetic field that has the potential to move other objects. Potential nuclear energy exists because of the relationships between subatomic particles, such as protons, electrons, and neutrons, in the nucleus of atoms.
Another of the common potential energy examples is gravitational energy. A falling object will accelerate thanks to kinetic energy. When the object hits the ground, this same amount of energy will be released as heat and sound in the collision. However, before the object falls, this amount of energy is stored as potential energy.
The amount of gravitational energy will depend on both the mass of the object and the height at which it is resting. If you move a book from one shelf to a higher shelf, the book's potential energy will increase. It may seem confusing that the same book can increase its potential energy without any physical changes. However, the increase in potential energy will come from and equal the energy you expend in lifting the book higher up.
