# Which one will turn the ceiling fan faster? Current, voltage, or power? [duplicate]

Which one of these things will turn faster the ceiling fan?

Is it the amount of electrons by unit of time passing through the engine, so is it current? Is it voltage, or is it the two that makes the ceiling fan turn faster so is it the power in watts?

For example if I pass in the same ceiling fan:

1. 5V 1A (assuming it accepts this voltage and current in it)
2. 1V 5A (assuming it accepts this voltage and current in it)
• Which will turn faster and make more wind?
• Will they turn at the same speed?
• I don't understand this, it does not help me... Commented Jun 20 at 7:39
• Two motors both designed to work on 5V 1A can have different rated speeds due to the winding design. Commented Jun 20 at 8:10
• @ nanash1 ans @Andy_aka : if you wish to close it as duplicate, it would be nice to find a true duplicate (OP is asking for an AC fan, you redirect to a DC motor, even if it's true that the answer is the same) Commented Jun 20 at 12:18
• @Sandro It's not clear to me that the question is about an AC fan. It's not stated anywhere in the question. We can only guess he means an AC fans because of this follow-up question about inverters. Imo the question makes even less sense for AC fans that's why I initially assumed he meant a DC fan. Commented Jun 20 at 13:05
• true, I was jumping to the conclusion that it is an AC fan, because I've never seen a ceiling fan that is DC powered (small fans, yes, like USB fans or fans inside electronics products). But it might make sens in some regions where people tend to use a lot more batteries/solar pannels. Commented Jun 20 at 13:27

For a given fan, you only have one degree of freedom: if you set a voltage, then there is only a single possible current (and a single possible power). And if you set a current, then there is a single possible voltage (and a single possible power). And if you set a power, then there is a single possible current and voltage.

If we simplify things and consider the fan as a fixed resistor R (quite inaccurate, but it will make explanations simpler), then you have:

• U=R*I
• I=U/R
• P = U*I=R*I²=U^2/R

So if you know R, then if you set one parameter (U (voltage), I (current) or P (power)), then you can deduce the other 2.

So basically, it is not possible to pass the same fan 5 V 1 A and 1 V 5 A.

For different fans, what basically matters is the power (U*I), and the efficiency (which depends on technology, the shape of the blades, the quality of the bearings, if the speed is close to the optimal speed, ...)

• Beat me to it :-) Commented Jun 20 at 8:01
• If you are using * in text to denote multiplication, you need to use backslash* or two of them will be used to italicize the text between the two *. MathJax is another way to do it. I've edited your answer accordingly. Commented Jun 20 at 8:20

There is a connection between current and voltage.
Thus, you can not feed 1 volt and make it draw 5 amps. This depend on the resistance of the motor.
If you feed it 5 volt and it draw 1 amp, then the resistance of the fan is 5 ohm.
If you feed it 1 volt and it draw 5 amps, then the resistance is 0,2 ohm.

Since the resistance of the motor doesn't change, the more voltage you provide, the more current will it draw.
If we take the 5 ohm from above, if you feed it 10 volt, it draws 2 amps.
If you feed it 15 volt it draws 3 amps.
If you feed t 20 volt, it draws 4 amps.

Amps (A) is voltage (V) divided bu resistance (R): A = V/R

And yes, the more voltage, and thus the more current it draws, the faster it goes.

• Unless stalled, a brushed DC motor is not a resistor, it has EMF when spinning. Commented Jun 20 at 8:22
• Okay, but why in a transformer DC to AC 12V et 220V when I increase the voltage, the current decrease to keep the same power ? Commented Jun 20 at 8:24
• @winny Yes, but due to the knowledge level the question indicates, I would not make the answer unnecessary complicated. Commented Jun 20 at 8:28
• @Moreless That's a complete different topic. The OP question is about drawing current, the transformer is a question about current that will be provided. Commented Jun 20 at 8:30