# dc motor

Discussion in 'Off-Topic' started by stivsence, Feb 26, 2010.

1. ### stivsence Thread Starter New Member

Feb 25, 2010
1
0
hi guys? you are doing a great job here.pls. I need help.
I attended a seminar on how to build a fueless generator.
A DC motor is one of my components,have seen severals only with the voltage rating but no rpm.how do i get this please?

2. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
I hope you didn't pay money to attend the seminar.

You can't get more power out of something than you put in. You can't even get the same amount of power (unity) out as you put in. You can get close to unity, but there will always be some losses.

If someone tells you that you can get something for nothing, they are either trying to fleece you, or just don't understand basic physics. That is why this forum doesn't participate in so-called over-unity type discussions

3. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
What might the RPM of the motor have to do with anything? A "fueless" generator is another name for a perpetual motion machine.

See the sticky notes at the top of this section for numerous explanations why perpetual motion machines (aka "overunity" devices) can't work. See if you can get a refund on any fees you may have paid.

4. ### BillB3857 Senior Member

Feb 28, 2009
2,399
348
The OP could be talking about wind or water power. I guess for a purest, wind and water could be considered fuel. Many DC motors can also be used as generators. To answer his original question, connect the motor to a DC source and measure the RPM In theory, if you spin the motor by mechanical means, it will produce the same voltage at that RPM. That is the general concept of Back EMF, or Counter EMF and is usually specified as Kv (K for constant, v for velocity) and is based upon voltage at 1000 rpm.

Apr 20, 2004
15,815
282