How Does Battery Configuration Affect DC Motor Speed?

[Brandon02]

Homework Statement

Hello, I am a 6th grade student trying to build a DC motor for the science fair. My hypothesis is that the dc motor will run faster if I place batteries in parallel versus batteries in a series. Is there an equation i can look at to explain what is happening? the mootr will be like the one found on youtube built by howtolou. thank you.

Homework Equations

The Attempt at a Solution

voltage constant = (V-IR)/rpm?

 

[phinds]

It will depend on the voltage required to drive the motor and the voltage of the batteries. For example, if it takes 20 volts to drive a particular motor, you can put a million 1.5 volt batteries in parallel and they will not run the motor. Sounds like you should study a bit of basic electricity before going any further.

It's a good project but without knowing a bit more of the basics you might find it overly frustrating.

 

[Brandon02]

Thank you Phinds
I understand a parallel set up will not increase the volts but a series will. Maybe my project should be about increasing voltage only. But if I make a dc motor like the one on Internet, why can't I just add enough battery to make it run and then experiment with more batteries added in a series?
Brandon

 

[phinds]

Thank you Phinds
I understand a parallel set up will not increase the volts but a series will. Maybe my project should be about increasing voltage only. But if I make a dc motor like the one on Internet, why can't I just add enough battery to make it run and then experiment with more batteries added in a series?
Brandon

Too MUCH voltage is worse than too little. Too little just means it won't run. Too much means it will burn out (or the batteries will). The right voltage and not enough current won't work either. You need a happy balance of series AND parallel to get the right voltage with sufficient current capability. If the batteries are big enough (enough current capability) for the motor in the first place then series will do. You need to know what the motor specs are and what the battery specs are.

 

[rezeew]

Hello, as a scientist, I am happy to assist you with your science fair project. First, let's address your hypothesis. Your hypothesis is that placing batteries in parallel will make the DC motor run faster than placing them in series. This is a great hypothesis to test, and it shows that you understand the concept of voltage and current in a circuit.

To explain what is happening, we can use the equation for voltage in a circuit, which is V = IR. V represents voltage, I represents current, and R represents resistance. In a series circuit, the voltage is divided among all the components, so each battery will only be providing a portion of the total voltage. This can limit the motor's speed. In a parallel circuit, each battery provides the same voltage, which can result in a higher total voltage and potentially a faster motor speed.

To further understand the relationship between voltage, current, and RPM (revolutions per minute), we can also use the equation P = VI, where P represents power. This equation shows that the power of a motor is directly proportional to the voltage and current. So, if you increase the voltage, you can increase the power and potentially the RPM of the motor.

As for the specific equation you mentioned, it seems like it may be a variation of the standard DC motor equation, which is V = kω, where V is the applied voltage, k is a constant, and ω is the angular velocity of the motor. This equation shows that the voltage applied to the motor is directly proportional to its speed.

I hope this helps you understand the science behind your project and provides some equations for you to explore further. Remember to always test and record your results to support your hypothesis. Good luck with your science fair project!