In this article we will discuss about the different forms of energy. Energy can manifest itself in many forms. Some of these forms are as follows:
(i) Mechanical energy:
The sum of the kinetic and potential energies in bulk is called mechanical energy. Kinetic energy is due to motion while the potential energy is due to position or configuration.
(ii) Internal energy:
The molecules of a body vibrate with respect to one another. These molecules have kinetic energy due to their motion and potential energy due to their attractions and repulsions. The sum of the kinetic and potential energies of all the molecules is called the internal energy of the body. As the temperature of a body increases, its internal energy also increases.
(iii) Heat or thermal energy:
A body possesses heat energy due to the random motion of its molecules. Heat energy is also related to the internal energy of the body. In winter, we generate heat by rubbing our hands against each other.
(iv) Chemical energy:
A stable chemical compound has lesser energy than its constituent atoms, the difference being in the arrangement and motion of electrons in the compound. This difference is called chemical energy. A chemical reaction is just the rearrangement of atoms. If the total energy of the reactants is more than the products, heat is released, and the reaction is exothermic. If the reverse is true, heat is absorbed, and the reaction is endothermic. When 1 kg of coal is burnt, it releases 3 × 107 J of energy.
(v) Electrical energy:
Electric charges and currents attract or repel each other, i.e., they exert forces on each other. Work has to be done to move charges with respect to one another. The energy associated with this work is called electrical or electromagnetic energy.
(vi) Nuclear energy:
Neutrons and protons attract each other very strongly at distances of order 10-15 m and bind together to form nuclei. The associated energy is called nuclear energy. Nuclear energy is released in the process of nuclear fission and nuclear fusion. In each of these processes, a part of the mass (called mass defect) is converted into energy in accordance with the Einstein’s mass-energy relation.