Law of Conservation of Energy

Law of Conservation of Energy talks about the energy of an isolated system; how the total energy (in any of its forms) gets conserved. When the system undergo a process change, the sum total of the energy quantum of the components remains same.

There are various forms in which Energy can manifest itself:Law of Conservation of Energy – Various Forms of Energy

• Thermal (Heat) Energy
• Sound Energy
• Light Energy
• Mechanical Energy
• Potential Energy
• Kinetic Energy
• Chemical Energy
• Magnetic Energy
• Electrical Energy
• Other Forms, such as
• Wind Energy
• Solar Energy
• Water Wave Energy
• Nuclear Energy (Fission, Fusion)

Statement of Law of Conservation of Energy

The total energy of a closed system is always constant. Energy can neither be created nor destroyed. However, energy can convert from one form to another. This is one of the many conservation laws of physics:

• Law of Conservation of Mass-Energy: This is actually a combination of both laws of conservation of Mass and that of Energy. But with demonstration of converting the mass to huge amount of energy, as in nuclear explosion, (E = MC²), this is now the law of conservation of Mass-Energy. This takes into account the Mass-Defect observed by physicists in nuclear reactions.
• Conservation of Linear Momentum
• Conservation of Angular Momentum
• Conservation of Electric Charge

Examples of Law of Conservation of Energy

Assume a mass (m) connected to a helical spring of spring-constant (k). The Potential and Kinetic Energies of the mass at any distance (x) from mean-position are given by:

$PE = \frac{1}{2} k x^2$

$KE = \frac {1}{2} k \left ( a^2 - x^2 \right )$

So, Total Energy = PE + KE = ${\frac{1}{2}} k a^2$ , which is constant!