# Perpetual Motion.

Hypothetically speaking of course-

For a machine to be perpetual;
Does it have to start its movement off its own energy / work from its own system?
Or does it simply have to sustain momentum-movement once its motion has started?

Ie) If I use an electric current which is employed from outside the system, to START the 'system of perpetual motion' is this still classified as a perpetual-motion-machine?

BTW: Im quite aware about the laws of thermodynamics, and dont want to argue about the unconventionality of perpetual motion.

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Janus
Staff Emeritus
Gold Member
There are two "classes" of perpetual motion. The first type just continues movement forever. The second supposedly allows one to extract energy from the device forever.

There is no requirement that the device initially start by itself.

Andrew Mason
Homework Helper
dx/dy=? said:
Hypothetically speaking of course-

For a machine to be perpetual;
Does it have to start its movement off its own energy / work from its own system?
Or does it simply have to sustain momentum-movement once its motion has started?

Ie) If I use an electric current which is employed from outside the system, to START the 'system of perpetual motion' is this still classified as a perpetual-motion-machine?
Like a superconducting magnet? A superconducting magnet is not a perpetual motion machine because it does no work (once the current is established).

A perpetual motion machine is defined as a machine that does work without any input of energy. It can start any way you like (but it will always end).

BTW: Im quite aware about the laws of thermodynamics, and dont want to argue about the unconventionality of perpetual motion.
It is not unconventional. Perpetual motion is very common (orbiting electrons, orbiting planets, stars). A perpetual motion machine, on the other hand, is not unconventional. It cannot exist (in our universe).

AM

Yeah, 'PERPETUAL MOTION MACHINE' thats prob' what i should have said.

Thanks for the replies.

James.

Andrew Mason
Homework Helper
BTW, there is another kind of perpetual motion machine that doesn't defy the law of conservation of energy but does defy the second law of thermodynamics. An example would be a ship that takes heat from the ocean to run its heat engines.

AM

Andrew, how did the bogus ship become colder than the ocean in the first place? Answer: Some one did more work on it then it could possibly extract from the oceans internal energy.

After one stroke of the engine, when the ship and ocean are at equilibrium temperature, how are you going to get any more energy out of the ocean? Answer, you have to do more work cooling he ship than you obtained from the oceans internal energy!

Andrew Mason
Homework Helper
Crosson said:
Andrew, how did the bogus ship become colder than the ocean in the first place? Answer: Some one did more work on it then it could possibly extract from the oceans internal energy.

After one stroke of the engine, when the ship and ocean are at equilibrium temperature, how are you going to get any more energy out of the ocean? Answer, you have to do more work cooling he ship than you obtained from the oceans internal energy!
Well, you wouldn't be cooling the ship. You would be cooling the ocean by adding work to transfer heat from the ocean to a hotter reservoir on board the ship and then trying to run a heat engine between the hot reservoir and the ocean. You can deliver much more heat to the hot reservoir than the work that you put in. That is quite permissible thermodynamically (so long as the first law is not broken).

But what you cannot do is extract more work out of that hot reservoir than the work that you originally put in. That would violate the second law of thermodynamics, but it would not violate the first.

AM

The question depends on whether PPM generate energy or not.

HI I have an experiment that may not be overunity but possibly close. So I was wondering if you would check what I wrote about it and let me know should it still be running after 8 days or not? Also catch me on yahoo in bpe1 as inhabitor2005 here is my experiment http://www.geocities.com/inhabitor2005/

brewnog
Gold Member
srdickens said:
HI I have an experiment that may not be overunity but possibly close. So I was wondering if you would check what I wrote about it and let me know should it still be running after 8 days or not? Also catch me on yahoo in bpe1 as inhabitor2005 here is my experiment http://www.geocities.com/inhabitor2005/
I read your page. I've decided that you're not a crackpot, merely ignorant. Disconnect the battery and tell me what happens.

srdickens, you are the first person I know to claim that a motor attached to a battery is a perpetual motion machine.

The reason this motor runs longer off of a single battery than your typical perpetual machines is surely because this cd-rom motor uses a very low voltage (high efficiency).

How can you observe "no power drain in the battery"? The energy in the battery is stored in the form of chemical potential; without measuring the number of disassociated ions (atoms that gave up an electron to your motor) I cant see how you determined how much the battery has drained.

Because no noticable reading on my meter, of course like the webpage explained I use an old needle type meter,,which can show slight errors. And because I have done many experiments and the longest that ran in relation to motors was along the lines of one motor turning another to recharge the battery,,and that one along with many others never ran but a few hours of non stop action with no noticable spin loss or battery drain..The point was that by running this long 8 days now to me is amazing. If you experiment in such areas and know how long motors last running non stop and you would have thought the same. But thanks for the reply.

You don't have a perpetual motor, see you still need energy to make it run as brewnog said. The reason why your motor is running so long is beacuse you have a magnet and that is probably giving some extra torque to your motor, it's still not a perpetual motion machine. There is resistance in everything which causes loss of energy that is why you would leave a fan plugged in if you wanted it to run. If there was no resistance in the wires that the fan used and no friction in moving the fan arms then you would need to plug it in only once and could unplug it and it would theoretically keep on going. However, since it'd have to be in a vacum it would cease to have a practical purpose, but it's impossible anyways.

The problem is that you are confused about the difference between voltage and energy.

As a battery drains its energy, the voltage in the battery does not change. This is because the way the chemical process in the battery works: the chemical reaction continues at the same rate (constant voltage) untill there is no more of the active chemical (out of energy).

Let me repeat, measuring the voltage does not tell you how much energy is in the battery.

The point was that by running this long 8 days now to me is amazing. If you experiment in such areas and know how long motors last running non stop and you would have thought the same.
Your are running a motor using batteries! There is nothing impressive about this, it is happening all around us in our technological world. Consider the watch on your wrist: it can run for years on just one battery! According to you, since the watch runs at a constant 0.5 volts, there is no power drain!

DaveC426913
Gold Member
If you want a machine that will run for days or weeks without stopping, get a pendulum clock. It's not perpetual motion, it's just efficient. Same with many other of these so-called PMMs.

right on crosson unless he was measuring the amps too. sorry if our answers disapoint you srdickens, but, we saved you from being embarresed when you would have sent your findings to be published. It seems as though you like experimenting maybe you should concentrate on learning some more physics, i wasn't trying to be derogatory, continue experimenting, but learn some of the principals as well.

brewnog
Gold Member
what said:
right on crosson unless he was measuring the amps too. sorry if our answers disapoint you srdickens, but, we saved you from being embarresed when you would have sent your findings to be published. It seems as though you like experimenting maybe you should concentrate on learning some more physics, i wasn't trying to be derogatory, continue experimenting, but learn some of the principals as well.
Spot on what, welcome.

Keep playing with those motors srdickens! I remember when I was about 10, running a motor off a battery, and driving a dynamo with the motor, then trying to disconnect the battery and feed the dynamo output into the motor.... It didn't work, but I learnt how to solder!

russ_watters
Mentor
Crosson said:
As a battery drains its energy, the voltage in the battery does not change. This is because the way the chemical process in the battery works: the chemical reaction continues at the same rate (constant voltage) untill there is no more of the active chemical (out of energy).

Let me repeat, measuring the voltage does not tell you how much energy is in the battery.
Clarification: the voltage does drop as you drain a battery, its just not a linear function to zero. HERE are the discharge profiles of 3 types of batteries. Only the NiCd appears flat over most of its range. I couldn't find an alkaline, but its discharge curve is steeper.

However, your point is still valid - over most of its life, you wouldn't notice a change in speed of the motor or voltage (especially on an analog volt-meter).