Hi falks,
as my name suggest, i am an absoltue beginner.
so therefore I'm going to ask you a stupid question again:
What defines the power of a DC motor ?
Is it the WATTs ?
Is it the VOLTs ?
Is it the AMPs ?
Or is it a combination of all ?
Second question: I amlooking for a strong DC Motor.. Strong enough to run two gears like you see on the photo.
Any suggestions ?
What gears need what motor..... Any tine little low voltage motor will turn those gears.
Describe the entire mission, what torque is needed and a lot more.
Please read the first topic telling how to get the best from this forum.
Your question lacks a lot...
Power is measured in watts. So a motor rated at a higher wattage is more powerful than a motor rated at a lower wattage.
HOWEVER, to generate those watts requires both volts AND amps. That's because:
power (in watts) = electrical pressure (in volts) * electrical current (in amps)
Therefore the motor will only generate its rated power if the power supply is capable of delivering the specified voltage at the specified current.
If the voltage from the power supply is too low, or it won't deliver the current that the motor requires, then the motor will not generate its maximum rated power.
Does that make sense?
It makes absolute sense sir, and absolute thanks you for nailing the right answer for my question. You have answered my question absolutely !! Thanks man.
I will mark your answer as "best".
I myself also had a thought, that WATTs is defines the motor power.
Thanks mate !
Torque is something being important most of the time.
yeah, but for a strong Torque, power is absolutely necessary, right ?
I know, I am an absolute beginner, but at least, I am a little fan of physics 
You know, electrical energy (produced by chemical reactions with coal, solar or nukes) is transformed to kinetic energy (DC MOTOR). An Torque is kinetic energy. So, therefore, WATT is the unit that counts. AMPs is defined by "moving electrons or ions, and VOLTS is defined by "electrikal potential between + and -".
Sorry, Amps is defined by "an amount of moving electrons or ions within a certain time".
A motor has a more or less fixed "resistance". In order to increase the power (Watts) one must increase the voltage so that the current can increase. You can't increase the current without increasing the voltage.
Almost. Earlier we said that electrical power (in watts) = volts * amps.
Mechanical power is also measured in watts, and is calculated using torque and rotational speed:
power (watts) = torque (Nm) * rotational speed (radians per second) (see note below)
So a motor may create a given power by producing a small torque at high rotational speeds or a high torque at low rotational speeds. There is an infinite number of torque/speed combinations that will produce the same power.
The design of the motor determines whether it is a high torque/low speed motor, or the other way round.
You can also alter the torque/speed combination using a gearbox. A gearbox might double the torque available from the motor, but at the expense of halving the speed, so the mechanical power remains unchanged.
Of course, a motor isn't 100% efficient, so maybe 95% of the electrical input power is converted into mechanical output power; the remaining 5% is lost as heat. The same is true of gearboxes: they actually reduce the mechanical power very slightly, converting some of it into heat due to internal friction.
Nm stands for newton metres. There are 2 x pi radians in one rotation. Therefore this formula can often be seen as:
power (watts) = torque (Nm) x 2pi revolutions per second
If you use "power" in the physicists sense, its watts.
In the colloqial sense you might mean watts, or newton-metres (ie torque).
The torque of a DC motor is proportional to the volume of the rotor (a fundamental limit of the properties of iron and copper lead to this).
The total power depends on the torque and speed multiplied together, generally larger motors have a lower top speed.
When designing a system driven by motors you need to calculate or measure the
wanted torque and speed, and only then select a motor and gearing - this is all maths, no guesswork is needed...
Adjectives don't help, numbers are what you use... "strong" means nothing, "0.7Nm at 4000rpm" means something.
Another good way to think of the fundamentals of volts and amps.
As stated, the power measured in watts but, you can think of the flow of electrons just like the flow of water where the voltage is the diameter across the pipe, and the current is the flow rate through it. That is why you measure voltage across two points, and you measure the current through two points.
Hopefully this helps a little with the terminology!
That information is completely incorrect.
A motor does not behave more or less like a fixed "resistance". You can increase the current by applying greater mechanical load on a motor. That usually increases the electrical power drawn by the motor.
Thinking of voltage as being like the diameter of a pipe is not at all helpful. Perhaps think of voltage as being a little like pressure in a pipe: but a physicist would not like that.
I've got to agree with @Archibald here: that explanation is misleading and confusing.
Absolutely they would, its a great analogy - not perfect, but intuitive and graspable...
I am always here to learn! (Just to pick your brain), (also @MarkT)
I certainly do not disagree with your statements and now I have more questions lol
If I were to look at current as (Coulombs / sec or simply, a "rate" ) and the voltage as a potential difference between two points (a diameter of cylindrical pipe analogous to the cylindrical wire with a diameter difference vs voltage difference)
Stick with me
Then, a large current "flow rate" with a small voltage differential can be looked at like a large water flowrate through a small diameter pipe. It would be easier to increase the size of the pipe I.E. increase the voltage, so I can decrease my flowrate I.E. lower the current
again, I know this is a discussion on how to grossly over-simplify an already abstract idea, so please dont take this as me trying to win! lol I am now more curious is all!
Am I wrong?
-JB
Wider short pipe has less resistance, thinner longer pipe has more resistance. You can crudely take the resistance as proportional to length / area.
(With copper (or any metal) wires the relationship is very accurate, electrical
resistance is proportional to length/area accurately, at a fixed temperature)
For low pressure at high flow you need less resistance, ie a wider and/or shorter
pipe (or wire for electrons).
Don't forget to take into account the Reynolds number for the electrons. 
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