What is Potential Energy?
To start with, energy in Physics is referred to as the ability to do work. It is a measure of an object or body’s capacity to do work. In Physics, work is said to be done when a force of 1 Newton moves an object through a distance of 1 meter in the direction of the force. The potential energy a system possesses is equal to the work done on the system. This form of mechanical energy can be transformed into other forms of energy. A typical example is as follows: when a ball is held above the ground and released, the potential energy is transformed into kinetic energy.
Potential energy is that energy which is stored in an object. The stored energy varies depending on the types such as physical, chemical or even electrical energy. The stored potential energy often stays in the object until the state of the object changes leading to the release of the energy. However, this release of the potential energy is controllable. When controlled, the energy can be used in tackling essential tasks. But in case the control is sudden, it can be very harmful.
It is the form of energy possessed by a body at rest. It is a result of the overcoming internal forces within an object relative to the various agitating external forces. In Physics, potential energy (PE) is said to be equal to a product of mass (m) in Kilograms, Acceleration due to gravity (g) in m/s2 and height (h) in meters.
That is, Potential Energy (P.E) = mgh.
This type of energy is present in every object which has a mass and position within a force field and has a kinetic energy of zero relative to other objects. There are various forms of potential energy. This includes Elastic potential energy, Nuclear energy, Chemical energy, Gravitational potential energy, and Electric potential energy.
However, it must be noted that there is usually a rapid conversion of energy from potential to kinetic when an object which originally possessed potential energy is set in motion, which consequently causes a change in position of the object.
In most cases, potential energy is just known to be a stored physical, chemical and electrical energy which is released upon triggering. Chemical energy is always stored in chemical bonds. The energy is then released when there is a chemical reaction. The physical energy is typically stored in cases where mass is put in a resting place which is above its zero height. Similarly, energy can also be physically stored when a structure is deformed or stressed.
Types of Potential Energy
Potential energy manifests itself in different ways. A typical example is found in electrically charged objects which possesses potential energy as a result of their position in an electric field. Explosive substances possess chemical potential energy that is transformed into heat, light, and kinetic energy when detonated. Nuclei in atoms have potential energy that is transformed into more useful forms of energy in nuclear power plants, referred to as Nuclear energy. The following are the major types of potential energy:
- Gravitational potential energy
- Elastic potential energy
- Chemical potential energy
- Electric potential energy
- Nuclear potential energy
- Intermolecular potential energy
Gravitational Potential Energy
This is the type of potential energy a body possesses by virtue of its position in a gravitational field. Generally, gravitational potential energy (V) is applied to an object near Earth’s surface, where the acceleration due to gravity is assumed to be about 9.8ms-2. Because the zero of gravitational potential energy can be taken at any point, the potential energy of a body at a height ‘h’ above the zero point could be said to be equal to the amount of work which would be required to lift the object to that height without any resultant change in kinetic energy.
Thus, the force (in Newton) required to lift the body is equal to the weight of the body. This is illustrated by the following relation:
PEgravitational = weight x height = mgh
U = -GMm/r
G = Gravitational constant
M = Mass of the attracting body
r = distance between the centres of the attracted bodies
- The negative potential energy that results from using this formula of gravitational potential indicates a ‘bound state’. In the bound state, a mass attracted to a larger body is trapped until enough energy is provided to enable escape of the body.
Elastic potential energy
This type of potential energy is one that results from the deformation of an elastic object. For example, when a string is stretched, the elastic potential energy is equal to the work done in stretching the spring. This depends on the spring constant ‘k’ and the distance of stretch ‘x’. According to Hooke’s law, the amount of force needed to stretch spring is directly proportional to the amount of stretch.
F = -kx
The work done to stretch the spring through a distance ‘x’ is:
Work = PE = 0.5kx2
Thus, when a spring is subjected to a stretch, elastic potential energy is stored within it, while at rest the spring is said to be at elastic potential equilibrium.
Chemical Potential Energy
This type of potential energy is one which is usually found within the chemical bonds of a substance. The release is often due to some chemical interactions between the various chemical elements of the substance possessing this type of potential energy. A typical example is found in gasoline which supplies power to combustion engines when burnt in a controlled manner, releasing large amounts of power and heat.
Another example of this type of potential energy is found in dynamites. Dynamite is majorly made up of nitroglycerin (a very unstable substance) which makes the dynamite prone to the explosion at the slightest physical shock. However, the unstable nature of nitroglycerin is greatly controlled when mixed with diatomaceous earth. Thus, dynamites prepared in this manner only explode when ignited, releasing large amounts of heat, nitrogen and other highly flammable gases.
Electric Potential Energy
It is a type of potential energy which is obtained from conservative Coulomb forces. It is associated with the configuration of a certain set of point charges within a well-defined system. It is often represented by UE
Where UE = C .V2/2
A very similar term ‘electrostatic potential energy’ is often used in the field of potential energy. However, electric potential energy is used in describing systems with time-variant electric fields, while electrostatic potential energy is used to describe potential energy present in systems with time-invariant electric fields.
As batteries are known for the production of electricity, the battery power is often generated due to chemical reactions within the battery cells. The chemical reaction triggers an imbalance of the electrons within the battery leading to the production of electric charge across the terminals of the battery. Therefore, batteries do store both electrical and chemical energy which are both forms of potential energy.
Nuclear Potential Energy
It is a type of potential energy associated with particles such as: protons and neutrons, within the nucleus of an atom. A strong, binding nuclear force exists between protons and neutrons within the nucleus, thus, large amounts of light and heat is often released when the nuclei of atoms combine to form a larger one through ‘nuclear fusion’ or break down into smaller nuclei through ‘nuclear fission’.
Intermolecular Potential Energy
This type of potential energy is one which depends on the magnitude of the forces of attraction or repulsion within the molecules of a substance as well as the relative position of the molecules. Due to the fact that molecules within substances exhibit randomness in orientation and configuration, it is often very difficult to make accurate measurements of the amount of this type of potential energy within a substance.
The Physical Potential Energy
This energy is usually studied in physics. It is that form of energy that is stored either as elastic or gravitational energy. The gravitational energy as a type of physical energy is as a result of the elevated body position, especially for bodies possessing mass. The amount of potential energy stored in such bodies will increase with an increase in their mass.
When the body is released leading to its mass dropping, the potential energy that it stores converts to kinetic energy, this happens as the mass gains speed since kinetic energy is that energy that is possessed by bodies in motion. The kinetic energy that is formed in this process is very useful or dangerous at the same time. It is helpful in the sense that it can be used to drive lots of piles into the ground. On the other hand, it becomes dangerous in case a big body such as bridges collapses.
Elastic energy as a type of physical energy is often stored when a structure deforms. A spring, for instance, has a regular shape. However, upon compressing or stretching it, it begins to store potential energy. When the spring is suddenly released, it can either cause damage or perform some tasks.
Similarly, the springs of a non-elastic wristwatch can be deformed through winding up the wristwatch giving room for the potential energy to power the watch. Another thing that stores the elastic physical potential energy is the elastic band. The band saves the potential energy upon stretching, and there is a possibility of the potential energy hurting when it breaks or when the stretching is released.
Examples of Potential Energy
There are lots of examples of potential energy depending on the types of potential energy in question. Listed below are some of the examples of potential energy with respect to the categories in which they fall.
Examples of Chemical Potential Energy
- A battery full of charge
- The candle wick
- An iron before rusting and before getting wet
- Chemical explosives
- Gasoline before ignition
- The potential photosynthesis on the green leaves before they receive sunlight
- Firewood before they are burned
- The fruit juice before fermentation
Examples of Electric Potential Energy
- Light bulbs turned off
- A non-working radio tower
- A turned off cell phone
- A turned off television
Examples of Physical Potential Energy
- A rock at the edge of a cliff before it falls
- The tree branches loosely hanging before it falls
- A stretched spring fitted in a pinball machine before it is released to move the steel ball
Examples of Thermal Potential Energy
- A swinging water pool before heating
- An empty chocolate mug before fitted with hot chocolate
- The dead organic matter which contains potential geothermal energy
- A geyser before it erupts
- An idling oven before turning on
Examples of Atomic Potential Energy
- Hydrogen atoms before the reactions
- Uranium atoms before fusion reactions