sfolk
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Simple Electric Motor - question about coil loop size

Postby sfolk » Mon Jan 24, 2022 11:42 am

My 7th grade daughter has tested out different coil loop sizes. (She is using C cell batteries plus the paper clips & the cylindrical neodymium magnets that came with the Electric Generator motor kit.) When she uses a highlighter (which is thicker than a Fine Point Sharpie marker) to create her coil wire loop (to be able to duplicate what’s recommended in the Science Buddies website & video), the coil loop is much too big to allow for 3 magnets to be stacked underneath the coil wire loop. Why might this be the case? We can provide a video or picture if you like.

Our 7th grade daughter is using C cell batteries plus the neodymium magnets & paperclips that came in the Electric Motor Generator kit. To determine what her one allowed variable should be for her to use, she has tried testing the project with just one battery & one magnet as her control, which work fine, and then she tried testing the same configuration with a second magnet & then with a second battery for her variable. We see very little increase in the speed of the coil wire’s spin when testing out both types of variables. (We do believe that a second battery helps the coil loop’s spin continue for much longer, though.) We have looked at & applied the appropriate troubleshooting tips. Are you able to share what the results of adding each of these 2 different variables OUGHT to be? (We are not allowed to add two different variables at the same time to her “control” configuration for her project.)
We are somewhat bewildered & are looking for any feedback that you are allowed to give. She is fine with telling the judges that her results were not typical or ideal. Please *feel free* to refer her (us) to any articles or posts that already exist “if appropriate.” We both want for her to do this super neat project justice!! We can provide videos as an example if you like.


Moderator note: I've combined your two posts about the Simple Electric Motor in one post. That way, the experts will see that the single post has not been answered and the experts will answer both questions! Thank you and best of luck to you and your daughter with this fascinating project!

Madeline

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Re: Simple Electric Motor - question about coil loop size

Postby AmyCowen » Wed Jan 26, 2022 12:01 pm

Hi Madeline - I am passing along some feedback from one of our scientists.

I am glad your daughter is excited about this project! It is fun to see the coil spin! I am sorry she is encountering some challenges. Below are a few things that might help:

For her first issue (the coil being too large to accommodate three magnets), try the following:
* Look at the opening in your paperclip (the loop where the axle fits through). Would making this loop smaller help to make the axle sit higher? If you find it is hard to bend the paper clips, the second option might be easier.

* A second solution is to attach the paper clips higher on the battery. Figures 14 and 15 in the project show the paper clip going under the battery terminals. This makes it easier to attach the paper clips. You can, however, attach the paper clips on or above the battery terminals as long as you keep good electrical contact. If you need to attach the paper clips so high that you lose the electrical contact, add some aluminum foil in-between. Aluminum foil is a good conductor so that should help re-establish the electrical connection.

I hope these tips can help raise the support for the axle just enough to fit the third magnet. Having the support higher will change the test results for one and two magnets as the magnets will be further away from the coil. It might be possible that, after the adjustments, the motor does not or barely rotates with one magnet. Magnetic fields become weaker the further you move away from the magnet. As the single magnet is now further away from the coil, it might not create a strong enough magnetic field to push the coil enough to make it rotate.

I hope this increased range in magnetic field strength will allow your daughter to see the change in rotational speed.

With respect to adding a second battery in series, the first item to verify is that the batteries are connected correctly. Look at Figure 22 of the project. I will describe the setup and hope this will help you verify your setup. In Figure 22, the paper clip in the back has electrical contact with the negative terminal of the first battery. The positive terminal of this battery (the first battery) is connected with a wire to the negative terminal of a second battery (the battery that does not have paper clips attached). A second wire connects the positive terminal of the second battery to the second support paper clip. What is not as clear in Figure 22 of the project is that, although both paper clips are attached to the first battery, only one of these paper clips has an electrical contact to the first battery. The second paper clip has electrical tape between the battery terminal and the paper clip (also shown in Figure 21). I am wondering if this confused your daughter. If your daughter finds it difficult to check her circuit, you can send us a picture and a description of her connections and I am happy to review it.

Connecting two full batteries this way will give you an increased current. It will not be double, but should definitely be larger. If that was not the issue, I would suggest trying with two new batteries, or to try with a 9 V battery (the batteries used in a smoke detector).

In theory, a larger magnetic field or a larger current both create a larger push on the coil. I hope this helps your daughter!

Let us know how it goes. If this does not solve the problem, maybe send us a few pictures. All the best!


I hope this information helps.

Amy
Science Buddies

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Re: Simple Electric Motor - (follow up) question about coil loop size

Postby sfolk » Thu Jan 27, 2022 2:48 pm

Thank you sooo much for your very helpful & detailed feedback!! It really does clarify things!!

She has 2 questions to help fill in some gaps about her project.

1. She understands that she’s needing to create a closed loop to accomplish what she’s trying to accomplish with the 2-battery set-up. She did in fact include / apply a piece of electrical tape in between the wire & the paper clip on the positive side of the first battery. Why does the piece of tape need to be applied IN BETWEEN the wire & the paper clip? Does this overly complicate the closed loop set-up, or does it create a *safety risk* (maybe too much current flow potential?) to allow the paper clip to touch both the terminal & the wire? (In other words… Why is “the tape being used outside the paper clip & the wire” ~NOT~ recommended?)

2. She first used the simplest set-up as depicted in the Science Buddies video (1 battery, 1 magnet) with a D battery (b/c the D battery was listed in the materials list in the video). (I then read the booklet that came with the kit to troubleshoot & read about the C battery being the best type of battery to use.) The coil wire was *very* hot to the touch (with the “D” battery), but she never experienced the coil wire being very hot at all when she used C batteries. Are you able to speculate what makes the coil wire too hot to touch sometimes but not other times? (A “D” battery likely has more power / current output than a “C” battery, but she doesn’t assume that it only depends on whether she uses a C battery or D battery. Under the Caution section on pg. 53 of the kit’s booklet, it talks about the possibility of the coil wire overheating. She & I both assume from this that the C battery “can” cause the coil wire to be too hot to touch when spinning above a fresh “C” battery. She would like to comment (in front of the judges) about why the coil wire is sometimes too hot to touch & sometimes not.

It would seem that for the coil wire loop to have a strong enough magnetic field to spin, then it would TEND to either always be pretty hot or never get hot, & she wonders what factor[s] cause the inconsistency of the temperature of the coil wire. (In her experience, a battery has to be fresh in order to get the motor / coil wire loop to spin, but the motor ~never~ gets too hot when she uses a “C” cell battery.)

Obviously if a motor (the coil wire loop) spins for a long while (more than 12 or 15 seconds), then the coil wire loop is *all the more likely* to get overly warm.

The answer might lie on how long the motor spins (as a result of a continuous electrical circuit) OR how fresh the battery is OR a D battery is “more likely” than a C battery to cause the coil to get very hot. [Maybe all of the above, but if so, then what would be the greater / stronger / more likely factor?] This issue falls under the “Risk & Safety” category of her presentation, so she wants to be able to explain this subtopic (& not just assume the reason for her inconsistent results) accurately.

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Re: Simple Electric Motor - question about coil loop size

Postby bfinio » Mon Jan 31, 2022 8:21 am

Hi sfolk,

I'm one of the staff writers here at Science Buddies and I'm going to chime in specifically about your second question (I have not done this exact experiment myself recently so I will check with one of our other scientists about the physical setup with multiple batteries for your first question).

Your daughter is on the right track about the explanation for C vs D batteries, and normally students would not learn about this until high school physics but it sounds like she is really engaged and wants to be able to explain to the judges, so this is worth explaining. Electrical circuits are described by an equation called Ohm's Law:

Voltage = Current x Resistance

you will usually see this abbreviated as V = IR (that's a capital letter "i", not a lowercase "L"). Voltage is the amount of "push" on the electricity. Current is the amount of electricity that is flowing. Resistance is how hard it is for electricity to flow through the wire. You can see from the equation that for example, for a fixed (constant) resistance, if you increase the voltage, then the current will also go up. As a rough analogy, think of water flowing through a pipe. For a constant pipe size (resistance), more pressure (voltage) will make more water (current) flow through the pipe.

So what does that have to do with your motor? The amount of current flowing through the wire depends on the resistance of the wire, the voltage of the battery, *and* something called the "internal resistance" of the battery (in other words, there is a little bit of resistance inside the battery itself, the battery is not "perfect"). The higher the battery voltage, and the lower the overall resistance, the more current will flow through the wire and the hotter it will get.

AAA, AA, C, and D batteries all actually have the *same* voltage, which is about 1.5 volts. However, bigger batteries generally have a *lower* internal resistance. As a battery is drained, its voltage drops *and* its internal resistance goes up, so the amount of current flowing through the circuit will decrease. Bigger batteries have a higher capacity (they hold more charge) so they can also provide more current for longer periods of time.

So, I realize that was a lot (remember, this is high school level physics!). Trying to recap at a 7th grade level and what you would tell a judge - the reason the motor spins faster and gets hotter with a D battery is NOT because the D battery has a higher voltage than the C battery - that is a common misconception. The voltages of the two batteries are the same, but the D battery has a lower internal resistance, so more current can flow. Scientifically, I would work on understanding the difference between voltage (the "push") and current (the "flow"), instead of lumping them both into "electricity," because mathematically they are two different things.

Hope that helps, please write back if it isn't clear and I can try to clarify further!

Ben

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Re: Simple Electric Motor - question about coil loop size

Postby bfinio » Mon Jan 31, 2022 8:26 am

* one more thing to add, somewhat related to your first question - when you connect two batteries end-to-end (this is called "in series") that DOES increase the voltage. So for example adding two 1.5 volt batteries in series gives you 3 volts, which again according to Ohm's Law will increase the current.

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Re: Simple Electric Motor - question about coil loop size

Postby bfinio » Mon Jan 31, 2022 1:09 pm

And here is the reply from my colleague regarding your first question:

My colleague already answered the second question. I only like to confirm her idea that the wire will get hotter when the motor runs longer.
For the first question:
The idea is to create a closed circuit with the two batteries are placed in series (this is the positive terminal of one battery is connected to the negative terminal of a second battery). A closed-circuit means there needs to be a loop in which the current can flow. I will first describe the loop. Starting with the negative terminal of the first battery, the current flows through the first battery to the positive terminal. ** From this positive terminal, it flows through the wire connecting the two batteries to the negative terminal of the second battery. After flowing through the battery to its positive end, it flows through the wire connecting the negative terminal of the second battery to the paperclip. The paperclip guides the current to the axle of the motor. When the side of the axle that has insulation stripped is touching the paperclip, the current can flow through the coils to the other end of the axle, and continue on flowing through the second paperclip down to the battery. As this paper clip makes electrical contact with the negative terminal of the first battery, the loop is closed.
The question related to the point in the loop indicated with two stars **. At that point, an electrical connection between the positive terminal of the first battery and the wire is needed, which means the bare end of this wire needs to touch the terminal of the battery. That is why the wire disappears under the electrical tape. Electrical current cannot run through this tape, so having the wire on top would not work, it would prevent current to flow from the battery to the wire.
The paperclip attached to this end of the battery, on the other hand, should not have electrical contact with the battery’s terminal as that would divert the current to the paperclip. in this loop, we want the current to flow first to the other battery, not through the paperclip just yet.
To prevent electrical contact, there is tape between the paperclip and the battery terminal at this end.
I hope I understood your question and answered it. If the explanation is unclear, or if it does not answer what your question, do not hesitate to get back to us.

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Re: Simple Electric Motor - question about coil loop size

Postby sfolk » Fri Feb 11, 2022 11:26 am

Thank you ALL *so much* for your clarifications & explanations!! The visual images that y’all have described are super helpful & greatly appreciated!!!
(I apologize for being sooo slow to hop back on here. Our house lost power during a recent winter storm for *2 days,* we have had company, & we are ~slowly~ getting back into the swing of things!!) My daughter’s science fair got moved to next week, & my daughter will be much more confident & prepared thanks to you all!! : D

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Re: Simple Electric Motor - question about coil loop size

Postby bfinio » Fri Feb 11, 2022 12:02 pm

No problem and happy we could help! Glad to hear the science fair got bumped back after you lost power. Please don't hesitate to write back if your daughter has more questions, or just to keep in touch to let us know how it went.

-Ben


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