Difference Between Mechanical Energy and Thermal Energy

Mechanical Energy vs Thermal Energy

Mechanical energy and thermal energy are two forms of energy. These concepts are very critical in fields such as mechanical systems, heat engines, thermodynamics and even biology. It is critical to have a clear understanding in these two concepts to master these fields. In this article, we are going to discuss what mechanical energy and thermal energy are, their definitions, the similarities and differences between mechanical energy and thermal energy.

Mechanical Energy

Energy is a non-intuitive concept. The term “energy” is derived from the Greek word “energeia” which means operation or activity. In this sense, energy is the mechanism behind an activity. Energy is not a directly observable quantity. However, it can be calculated by measuring external properties. Energy can be found in many forms. Mechanical energy is one such form of energy. Mechanical energy can be divided into two different types of energies. Kinetic energy is the form of energy that causes movements. Potential energy is the form of energy that occurs due to the placement of the object. The basic property of mechanical energy is that it always causes a directed, non-random movement of the object as a whole. If no external forces, except for the conservative force, are acting upon an object, placed inside a conservative force field, the total mechanical energy of the object is constant. More simply, the law of conservation of energy states that in an isolated system, which is only subject to conservative forces, the mechanical energy is constant. Potential energy can take forms such as gravitational potential energy, electric potential energy and elastic potential energy. In a conserved system, only energy conversions are possible. When the potential energy is increased, the kinetic energy will go down and vice versa.

Thermal Energy

Thermal energy also known as heat is a form of internal energy of a system. Thermal energy is the cause for the temperature of a system. The thermal energy occurs due to the random movements of the molecules of the system. Every system having a temperature above absolute zero has a positive thermal energy. The atoms themselves do not contain any thermal energy. The atoms have kinetic energies. When these atoms collide with each other, and with the walls of the system, they release thermal energy as photons. Heating such a system will increase the thermal energy of the system. Higher the thermal energy of the system higher will be the randomness of the system.

What is the difference between thermal energy and mechanical energy? • Mechanical energy is the ordered movement of the molecules as a single unit. Thermal energy is the random movement of the molecules. • Mechanical energy can be 100% converted to thermal energy, but thermal energy cannot be fully converted to mechanical energy. • Thermal energy cannot do work, but mechanical energy can do work. • Mechanical energy has two main forms, namely kinetic energy and potential energy. Thermal energy has only one form.