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Energy, defined as the capacity of a body to carry out work, can be of various types, such as thermal energy, mechanical energy, kinetic energy, potential energy, etc. In physics, we talk majorly about kinetic energy and potential energy. Kinetic energy is the energy of the body by virtue of its motion. Potential energy exists due to the object’s shape or position. Energy can be converted from one form to another, like in the case of a pendulum. A pendulum has maximum kinetic energy at its mean position and maximum potential energy at the extreme ends. Like kinetic energy is of various types (rotational, vibrational, and translational), potential energy can also be classified into various types.
Potential energy
Potential energy is the energy of a body by virtue of its position or shape. Its unit is the same as any other form of energy, Joules (J).
Potential energy is broadly of two types – gravitational potential energy and elastic potential energy. However, when we dig deeper, there are various other types of potential energy.
Five different types of potential energy are mentioned as follows:
- Gravitational potential energy
- Elastic potential energy
- Magnetic potential energy
- Chemical potential energy
- Electrical potential energy
Gravitational potential energy
Gravitational potential energy is the energy of the body due to its height. It is called so because it exists because of the Earth’s gravitational pull on the object. It is the product of mass, acceleration due to gravity, and the height at which the object is placed.
In mathematical terms, V = mgh (m is the mass in kilograms, g is the acceleration due to gravity, and h is the height in meters).
Hence, the SI unit of gravitational potential energy = kgm2s-2 or Joules (J)
We have to apply force against gravity to pull an object up to a certain height from the ground level. The applied force is parallel to the object’s gravitational force (Fg).
Elastic potential energy
It is possessed by a body by virtue of its shape. In the example of a bow and an arrow, an unstretched arrow only placed on the bow has no energy. As we start stretching it, it gains elastic potential energy.
The more an object is stretched, the more elastic potential energy it gains.
The formula for elastic potential energy can be expressed as follows:
U= 0.5kx2; k is the spring force constant and x is the stretch length
(Here, force, F = kx).
Sometimes, x is used in place of x, representing the displacement from the mean position.
Hooke’s law, which is used to arrive at the final formula, states that the spring force is directly proportional to the displacement of the ends of the spring from their respective mean positions. Basically, the more the stretch, the more the displacement from the mean position, and the higher the spring potential energy.
The following are the examples of the objects that can store elastic potential energy:
- Bow and arrow: When the arrow is drawn, it has potential energy.
- Sponge: Squishing a sponge stores elastic potential energy.
- Diving board: Before a diver jumps into the water, the diving board is bent. It stores elastic potential energy.
Chemical potential energy
Every matter consists of molecules that are bonded together by chemical bonds. The energy possessed by those bonds is termed chemical potential energy. It is possessed by atoms and molecules.
It can be transformed into other forms of energy, like mechanical energy. A prime example of this is gasoline, a hydrocarbon like methane. The carbon-hydrogen bonds of methane possess chemical potential energy. When methane is burned, it generates a considerable amount of energy which can be used to power a vehicle.
Electrical potential energy
It can be defined as the energy required to move a point charge under the influence of an electric field.
Opposites attract. A positive charge would be attracted to a negative charge. In a negatively charged electric field, force is required to move a positively charged particle away from its influence. That force is stored in the charge in the form of electrical potential energy. The positive charge uses it to go back to the electric field region when the external force is removed.
Magnetic potential energy
Every magnet has two poles – north and south. Two magnets exert a magnetic force on each other; as a result, magnetic potential energy is stored in them. For example, two magnets are attracted to each other. An external force is required to separate them, which would be stored in the magnets in the form of magnetic potential energy.
Conclusion
Potential energy is possessed in a body by virtue of its position or shape. The SI unit is Joules. The dimensions are [ML2T-2]. There are various types of potential energy that exist. The most important ones are gravitational potential energy and elastic potential energy, which can be easily determined using the formulae discussed above. But, there are chemical, electrical and magnetic potential energies too. All of them can be converted to other forms of energy as and when required.
