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Science of the Perpetual Motion Machines

Prachi Patkar Feb 8, 2019
Perpetual motion machines, though nonexistent in reality, are those machines which are known to operate without any supply of energy. This post sheds light on what a perpetual motion machine actually is, and why it is impossible to produce this type of machine.

Did You Know?

Scientists tried creating the perpetual motion machine, until the law of conservation of energy was devised in the year 1847. One of the machines that was created includes making use of the force of gravity to turn a wheel.
In Physics, the branch of thermodynamics deals with the conversion of energies into different forms. According to the laws of thermodynamics, the total energy of any isolated system remains constant. It can be translated from one form to another, but it can neither be created nor destroyed. Every machine should follow these laws in order to run.
In the upcoming sections, we shall understand what perpetual motion actually is, and whether machines can be created using this concept.

Perpetual Motion

Before learning about this machine, let us understand basics of perpetual motion. This type of motion continues without any supply of energy from outside sources. However, it is difficult to identify any motion as fully perpetual.
Consider a simple example, in which the celestial bodies rotate/revolve in the space. Their motion may be seen as ceaseless, however, they are subjected to many forces, such as gravitational force. This fact implies that the motion of celestial bodies is not perpetual.

Perpetual Motion Machine

The word perpetual means 'indefinite and uninterrupted'. Just as the name suggests, this machine, once set to move, keeps running continuously without the need of energy consumption. Thus, a perpetual motion machine is defined as a hypothetical machine that works without absorbing energy.
Although this concept was researched upon by a number of scientists, it could not be formulated in the real world. This machine is supposed to act as a boundless source of energy which is readily available.

Classification of Perpetual Motion Machines

Perpetual motion machines can be further classified based on the laws of conservation of energy.

► The first type of machine runs and produces energy without absorbing energy. Thus, we can conclude that it violates the law which states that energy can never be created nor destroyed.
► The second type of machine converts thermal energy into mechanical energy on running. The amount of thermal energy equals the amount of mechanical energy created.
► The third type of machine rules out any forces that lead to energy loss. This force is frictional force. If there is no dissipation of energy due to any force, it leads to continual functioning of the machine. However, the functioning of this machine will be restricted to energy storage, and not energy supply.

Example Explaining the Perpetual Motion Concept

The leftmost red-colored ball strikes the ball next to it, which in turn strikes the one next to it, and so on. In this process, energy gets channelized from one ball to the other in the order of their arrangement.
► Each ball strikes the one next to it. Thus, friction is caused, which leads to loss in the energy of the system. Gravitational force acts on this system too.

► When one ball strikes the other, sound energy is produced. Sound energy is a type of energy that is lost in the process.
► This machine, if not placed in a vacuum, causes friction with air. Though the magnitude of the air friction is really low, it cannot be ignored.

Since this machine violates the laws of energy conservation, it cannot be considered a perpetual motion machine.

Is it Possible to Create a Perpetual Motion Machine?

Any object continues to remain in motion unless disturbed by an external force. Consider two objects placed in an orbit. They are known to remain in motion unless interrupted by a third object. Consider a machine running without absorbing energy. It can run endlessly, provided no energy is lost. Let's consider a few ways in which energy can be lost.
No two parts should rub against each other.
The parts of a machine come in contact with each other while the machine runs. Thus, the parts offer resistance to each other. This is called friction. During friction, some of the energy is wasted in the form of heat.
This results in the reduction in the total amount of energy. According to the working principle of the perpetual motion machine, the amount of energy must not change for it to work.
The machine must not make any sound while running.
It is obvious for any machine to produce sound due to the contact between its different parts. Sound is a type of energy. Thus, if a machine makes sound while working, it loses energy. A machine cannot be considered a perpetual motion machine if it loses energy anytime during the course of its operation.
The machine to be run should be placed in a vacuum.
If the machine is not placed in a vacuum, air comes in contact with its parts, and causes friction. Though the energy that is lost in this type of friction is quite low, it is still something that cannot be ignored.
It is highly impossible for any machine to run continuously and produce kinetic energy, without actually absorbing energy from any external sources. Frictional energy and sound energy is definitely produced when various parts of the machine come in contact with each other while the machine is operating.
The energy produced is lost. This deficit in the amount of energy ceases the working of the perpetual motion machine, which is why a perpetual motion machine is impossible to create.
None out of thermal, chemical, or mechanical energy can be used to make a perpetual motion machine work. To summarize it all, this machine is hypothetical. Taking into account the fact that its working violates the first two laws of thermodynamics, it is highly impossible to produce it.