# Perpetual motion

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## Perpetual motion

The expression perpetual motion, or perpetuum mobile, arose historically in connection with the quest for a mechanism which, once set in motion, would continue to do useful work without an external source of energy or which would produce more energy than it absorbed in a cycle of operation. This type of motion, now called perpetual motion of the first kind, involves only one of the three distinct concepts presently associated with the idea of perpetual motion.

Perpetual motion of the first kind refers to a mechanism whose efficiency exceeds 100%. Clearly such a mechanism violates the now firmly established principle of conservation of energy, in particular that statement of the principle of conservation of energy embodied in the first law of thermodynamics. (Indeed, the first law of thermodynamics is sometimes stated as “A perpetuum mobile of the first kind cannot exist.”). See Conservation of energy

Perpetual motion of the second kind refers to a device that extracts heat from a source and then converts this heat completely into other forms of energy, a process which satisfies the principle of conservation of energy. A dramatic scheme of this type would be an ocean liner, which extracts heat from the nearly limitless oceanic source and then uses this heat for propulsion. This type of perpetual motion is, however, precluded by the second law of thermodynamics which is sometimes stated as “A perpetuum mobile of the second kind cannot exist.”

The third type of perpetual motion is, in contrast to the two types described above wherein useful output was the goal, merely a device which can continue moving forever. It could result in actual systems if all mechanisms by which energy is dissipated could be eliminated. Since experience indicates that dissipative effects in mechanical systems can be reduced, by lubrication in the case of friction, for example, but not eliminated, mechanical perpetual motion of the third kind can be approximated but never achieved. An example of a genuine case of this kind occurs in a superconductor. If a direct current is caused to flow in a superconducting ring, this current will continue to flow undiminished in time without application of any external force. See Superconductivity, Thermodynamic principles

References in periodicals archive ?
If we had continued as a nation to act on the long-term good, we would be a long way by now toward resolving our perpetual energy crisis.
Oil and natural gas company Perpetual Energy Inc (TSX:PMT) reported on Tuesday the launch of a new reserve-based credit facility agreement and Replacement TOU Share Margin Loan agreement to fund its growth-oriented capital programmes.
Perpetual Energy Inc (TSX:PMT), an oil and natural gas exploration, production and marketing company, has signed a new reserve-based credit facility agreement.
ISLAMABAD -- Islamabad Chamber of Commerce and Industry (ICCI) Tuesday said LNG import was great achievement of the government that would pave way for resolution of perpetual energy crisis in the country.
In an effort to advance clean energy access and technology, Masdar is deploying pioneering renewable energy projects across the globe; including Shams One, a 100MW concentrated solar power plant in Abu Dhabi; London Array, a 1 GW offshore wind farm in the United Kingdom; and Gemasolar, a 20MW concentrated solar plant with innovative storage technology enabling perpetual energy supply to the grid.
To deliver the solar energy system without upfront cost to the diocese, Photon partnered with an independent power producer, Perpetual Energy Systems, a Chicago-based firm, 'which paid for the solar equipment and will sell the diocese the power it produces under a 25-year solar services agreement.
Perpetual Energy Systems (PES), a financier and developer of solar-powered renewable energy systems, and Foster's Wine Estates Americas, a subsidiary of Foster's Group in Australia, today announced activation of four solar installations -- including the largest solar energy system installed at a United States winery.
What was intended to be just a green truck wash may have turned into the closest thing to a perpetual energy system the world has ever seen
Canadian energy company Perpetual Energy Inc (TSX:PMT) revealed on Wednesday that it has entered into a definitive agreement to sell its 30% partnership interest in Warwick Gas Storage LP (WGS LP) for USD20m, on or around 25 May 2016.
Islamabad -- Islamabad Chamber of Commerce and Industry (ICCI) on Tuesday said LNG import is great achievement of the government which will pave way for resolution of perpetual energy crisis in the country.
Compton Petroleum Corporation, Pengrowth Energy Corporation, Perpetual Energy Inc.
Perpetual Energy Inc (TSX:PMT), an independent natural gas producer based in Calgary, Alberta, Canada, has announced its operating results for the second quarter of 2011.

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