Perpetual Motion Machine of Third Kind (PMM 3)

A Perpetual Motion Machine of the Third Kind (PMM-3) is a hypothetical device that, once started, continues to operate forever without any energy input because it is assumed to have no energy losses (no friction, no air resistance, no electrical resistance, no material damping). Unlike other perpetual motion claims, a PMM-3 does not necessarily create energy or convert heat completely into work—it simply assumes a system with perfect efficiency and zero dissipation.

How PMM-3 Relates to Thermodynamics

PMM-3 violates the spirit of the Second Law of Thermodynamics.
The second law states that in any real process, entropy increases and energy degradation occurs due to irreversibilities like friction and resistance. Because of this:

• Mechanical systems always lose energy to friction and wear

• Electrical systems lose energy as heat due to resistance

• Fluid systems lose energy due to viscosity and turbulence

• Magnetic systems have hysteresis and eddy current losses

A PMM-3 assumes all these losses are zero, which is physically impossible.

Typical Imagined Examples of PMM-3

1. A perfectly balanced wheel spinning forever in a vacuum with frictionless bearings

2. A pendulum oscillating indefinitely without air resistance

3. An electrical loop with zero resistance current flowing forever

4. A magnetically levitated rotor spinning endlessly without drag

These examples ignore unavoidable microscopic and material losses present in real systems.

Why PMM-3 Is Impossible in Practice

Even with advanced engineering:

• Bearings always have microscopic friction

• Materials have internal damping

• Vacuum cannot remove all forms of resistance

• Superconductors remove electrical resistance but still face magnetic and thermal limits

• External disturbances (vibrations, temperature changes) introduce losses

Thus, motion always decays with time unless energy is supplied.

Difference from PMM-1 and PMM-2

Practical Insight for Engineers

While PMM-3 is impossible, the idea is useful. Engineers strive to:

• Reduce friction (better bearings, lubrication)

• Reduce electrical losses (high-conductivity materials)

• Reduce aerodynamic drag (streamlining)

• Improve insulation to limit heat loss

The goal in real engineering is approaching ideal efficiency, not achieving perfection.

Conclusion

A Perpetual Motion Machine of the Third Kind is a theoretical concept that assumes a system with zero energy loss, allowing it to run indefinitely after an initial start. In reality, due to unavoidable irreversibilities explained by the Second Law of Thermodynamics, such a machine cannot exist.

However, studying PMM-3 helps engineers understand the importance of minimizing losses and designing highly efficient mechanical, electrical, and thermal systems.