----perpetual motion machine

----perpetual motion machine Group members: Xiaoting Pang Boming Yang Zhou Fang Mengxi Song A great exploration

Perpetual motion describes hypothetical machines that operate or produce useful work indefinitely and, more generally, hypothetical machines that produce more work or energy than they consume, whether they might operate indefinitely or not. What’s perpetual motion machine?

There is undisputed scientific consensus that perpetual motion would violate either the first law of thermodynamics, the second law of thermodynamics, or both. Machines which comply with both laws of thermodynamics but access energy from obscure sources are sometimes referred to as perpetual motion machines, although they do not meet the standard criteria for the name. Perpetual motion machine

The classification A perpetual motion machine of the first kind A perpetual motion machine of the second kind

The first kind A perpetual motion machine of the first kind produces work without the input of energy. It thus violates the first law of thermodynamics: the law of conservation of energy. The law of conservation of energy is an empirical law of physics. It states that the total amount of energy in an isolated system remains constant over. A consequence of this law is that energy can neither be created nor destroyed: it can only be transformed from one state to another. Hence, it is impossible for a machine to do the work infinitely without consuming energy.

Examples of first kind perpetual motion machine Overbalanced Wheel Float Belt Capillary Bowl

Overbalanced Wheel The "Overbalanced Wheel". It was thought that the metal balls on the right side would turn the wheel because of the longer lever arm. But! Since the left side had more balls than the right side, the torque was balanced and the perpetual movement could not be achieved.

The Float Belt The yellow blocks indicate floaters. It was thought that the floaters would rise through the liquid and turn the belt. However pushing the floaters into the water at the bottom would require more energy than the floating could generate!

The Capillary Bowl The "Capillary Bowl". It was thought that the capillary action would keep the water flowing in the tube. But since the cohesion force that draws the liquid up the tube in the first place holds the droplet from releasing into the bowl, the flow is not perpetual.

The second kind A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However it does violate the more subtle second law of thermodynamics. The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics.

Example: Carnot heat engine Carnot engine diagram (modern) - where heat flows from a high temperature TH furnace through the fluid of the "working body" (working substance) and into the cold sink TC, thus forcing the working substance to do mechanical work W on the surroundings, via cycles of contractions and expansions.

Second Law of Thermodynamics: It is impossible to extract an amount of heat QH from a hot reservoir and use it all to do work. Some amount of heat QC must be exhausted to a cold reservoir. This precludes a perfect heat engine.

Although the perpetual motion machine has been proved a failure, people still attempt to improve their way to use energy. We try to decrease the energy wasted during the processes of energy transaction and transportation so that we can use it more effectively.

The attempt to improve our energy system

The wind power Solar energy hydropower

Reference • http://en.wikipedia.org/wiki/Perpetual_motion • http://www.kilty.com/pmotion.htm#Section4

Thank you for your time! 04.2011 Group members: Zhou Fang Xiaoting Pang Boming Yang Mengxi Song

----perpetual motion machine