Just a sideways diversion thought:

With everything everyone has thrown at you, you are sort of in a position of perhaps making a significant part project's presentation about how to design experiments to test your hypothesis. That is really a HUGE part of a lot of scientific work, Often the thing you are trying to evaluate isn't very complex conceptually, but trying to work out a way to actually do the evaluation in a way that produces trustworthy data can be very difficult. Demonstrating that you can get your mind around those sorts of issues, even if you can't come up with really good ways of handling the issues, shows people who really do science that you have the makings of a scientist. (Conversely, I've seen lots of cases where some company goes to a lot of effort to gather data when my question has been - OK, you have a bunch of data - now what do actually do with it?)

==
On TV programs and in movies you sometimes see people doing some sciencey thing and declaring that their experiment failed. Most of the time, what actually happened is that the experiment itself worked as it was intended to, but the result wasn't as expected. That isn't a failed experiment.

 

Things to consider:

What are the equation for the charging time of a capacitor if there is resistance in the circuit?
If there is resistance in the circuit, what does a plot of the voltage on the capacitor versus time look like?
Does the shape of the curve suggest anything about what voltage you might use for your time measurement point in terms of how consistent you can be if you have to evaluate when the charging has reach some fraction of "completion?'
Where would there be resistance in the circuit? Will it be consistent from one test to another?
How would you quantify that resistance?
How long does it take a capacitor to charge to a voltage equal to the supply voltage if the supply is "ideal"- can deliver infinite current?
Is your voltage source reasonably like and ideal source? (Can you put together a test circuit and actually record how the voltage on the capacitor changes to try to assess this? e.g. with a digital oscilloscope?)
How will you determine the actual value of the capacitor being tested? Do you know about component "tolerance?"

And the big one: Why is this matter of interest? Is it purely "academic" or is there some practical importance?

A warning: solid tantalum capacitors do not "like" being charged very rapidly with high current. They have a tendency to fail short-circuit. Some types actually have built in fuses to prevent major problems if the cap fails short-circuit.

This is for a school science fair experiment.

 

Just a sideways diversion thought:

With everything everyone has thrown at you, you are sort of in a position of perhaps making a significant part project's presentation about how to design experiments to test your hypothesis. That is really a HUGE part of a lot of scientific work, Often the thing you are trying to evaluate isn't very complex conceptually, but trying to work out a way to actually do the evaluation in a way that produces trustworthy data can be very difficult. Demonstrating that you can get your mind around those sorts of issues, even if you can't come up with really good ways of handling the issues, shows people who really do science that you have the makings of a scientist. (Conversely, I've seen lots of cases where some company goes to a lot of effort to gather data when my question has been - OK, you have a bunch of data - now what do actually do with it?)

==
On TV programs and in movies you sometimes see people doing some sciencey thing and declaring that their experiment failed. Most of the time, what actually happened is that the experiment itself worked as it was intended to, but the result wasn't as expected. That isn't a failed experiment.

Well, I mean. quite frankly, the teacher has a 200 other students to give a grade to. She's not gonna go digging into every single thing about capacitors. I am going to use alligator clips to feed readings into an oscilloscope as the capacitor is being charged. I will time it to see how long it takes to reach 1.49v (because never 100% charge, right?). For my grade level, I think its pretty advanced equipment that I'm using, so the teacher isn't drop bricks about how I got my data.

 

So, just to clarify, looking for the the cap that could reach the max faster, is the same as looking for the one with the lowest ESR?

Hello again and thanks for the question,

Yes as a start. Comparing the same values for each capacitor family should tell you something because one time constant is:
T=R*C

and so with the cap ESR we get of course:
T=ESR*C

There is also such a thing as ESL which would be the series inductance and that would cause a delay in charging too, but it may not be as significant as the ESR. To tell you the truth, this isnt something we do every day because normally we look for the appropriate type of cap FIRST and then look for an acceptable ESR. A question that arises for example is what happens if we determine that cap X123 made by Panasonic is the fastest to charge, and then next week they come out with a better one X123A and that is faster.

What school grade year is this for?

 

Someone in your school has not thought this through thoroughly or does not understand electronic circuitry.
Let us examine the comments provided in this thread so far (and some additional ones) that will make practical measurements very difficult.

1) ESR is a major contributing factor that will appear as differences in capacitor performance.
2) Theoretical and practical values of ESR are very small, less than 0.01Ω for ceramic capacitors.
3) Your connecting wires while conducting an experiment will have series resistances comparable or even greater than the ESR.
4) In order to charge a capacitor you will need a voltage source which will have resistance. This might be larger than the ESR of the capacitor under test.
5) The variation (tolerance) of the capacitance values may dominate any variation you observe in your measurements.

 

5) The variation (tolerance) of the capacitance values may dominate any variation you observe in your measurements.

Excellent point Mr Chips.
SG

 

Excellent point Mr Chips.
SG

@ebp said it first in post #18.

 

@ebp said it first in post #18

Stand corrected, still an important point one would hope the TS understands.
SG

 

Hi,

Yes there are many practical considerations when doing this in real life.

I might suggest FAKING it. This wont be the real thing, but can be said to mimic the true real life behavior of capacitors. It wont help find the real life capacitor in question, but it will show the idea behind how to find it which is also an interesting query.

What you could do is set up the experiment with quality caps that have KNOWN fixed resistors in series with them, then show which one charges the fastest. You'll have to hand pick the capacitors and use resistance values that are different enough so that they cause differences in the charge times that is easily measured with a regular scope or something. If you wanted to though, you could slow down the charge to the point where it can be seen on a meter. That would be stretching the concept out a bit but would still retain the idea.
Just a suggestion though.because i dont think you have the means to measure the real thing properly.

I asked about the school grade because that has a lot to do with the choice of experiment.

 

Hello again and thanks for the question,

Yes as a start. Comparing the same values for each capacitor family should tell you something because one time constant is:
T=R*C

and so with the cap ESR we get of course:
T=ESR*C

There is also such a thing as ESL which would be the series inductance and that would cause a delay in charging too, but it may not be as significant as the ESR. To tell you the truth, this isnt something we do every day because normally we look for the appropriate type of cap FIRST and then look for an acceptable ESR. A question that arises for example is what happens if we determine that cap X123 made by Panasonic is the fastest to charge, and then next week they come out with a better one X123A and that is faster.

What school grade year is this for?

8th grade

 

Everyone,
I think I found my hypothesis,

If a these capacitors are charged at 1.5 volts, then the tantalum will reach its max capacity the fastest.

This is because the tantalum has a small head, so it is easier for it to charge. Additionally, in general (I think) tantalum has a small ESR.
Can anyone confirm whether my hypothesis is a good one, and my explanation is correct?
Additionally, I made up a small experiment to see if my test will work. And it did!

 

I won't say good or bad. For 8th grade, the judge will probably not be too picky. However, review post #11, particularly the second part.

Your hypothesis is a guess based in part on a non-electronic characteristic (size). As an alternative,consider giving the standard equation for charging a capacitor and then hypothesis that all capacitors should charge at the same rate based on that equation.* Then add that capacitors are not perfect. They vary in tolerance and other characteristics, such as ESR and dielectric absorption as mentioned above. Then define your experiment is to determine whether actual components vary. Your null hypothesis is that there is no difference.

Some specifics:
1) Your original hypothesis that tantalums (BTW they are electrolytic too) charge faster. That is still a guess or opinion. That may lead you to using one-tailed analysis of only the tantalums versus "others." Strictly, you won't be able to show they charge slower, only "not faster."

2) The alternative suggests they are the same. That means you need to test whether they are faster or slower (two-tailed) and include all three versions.

*Edit: Of course, you cannot show they are the same. What you show is that you did not detect a difference.

 

If I were a judge, I would be looking for attention given to the various sources of measurement errors, and how they affect the confidence in the results. Artifacts due to experimental methods is one of the biggest problems in science A "demonstrated effect" in the lab is dime-a-dozen. Actual progress comes from eliminating every imaginable explanation other than the remaining hypothesis.

The judges, if they come from a science background, will know this. Most students (and many lower-tier researchers) don't think this way, so it's a way to get a leg up on your competition.

 

This is because the tantalum has a small head, so it is easier for it to charge. Additionally, in general (I think) tantalum has a small ESR.

You need to explain why you think that a small headed capacitor will charge faster than a larger headed version. Also, if you "think" that a particular capacitor has a small ESR, how are you planning on confirming it?

 

Well, I suppose all of you are right. Correct me if I'm wrong, but your saying that with the theories in mind, they shouldn't differ, ignoring ESR (Because T=RC, right?) Also, the ESR's would be discovered during testing, so it's appropriate to ignore it when making my hypothesis, correct? (rules are you need to have hypothesis before testing) So therefore my hypothesis should be:

If these capacitors are charged under 1.5 volts, then they should all reach maximum capacity in approximately the same amount of time.

Can anyone explain all of the information that has been thrown at me, as I am just a kid, who isn't entirely sure what all of you are saying about how my hypothesis should be formulated, in if/then format (don't get me wrong, I really appreciate the help), or how I should do my testing?

 

Must your project be on capacitors?

 

Does your project must be on capacitors?

Well, I chose it, and the teacher approved, and I'm sorta stuck with it. I mean, I'm just looking for advice on my hypothesis, I can definitely carry out the test.

 

Well, I chose it, and the teacher approved, and I'm sorta stuck with it. I mean, I'm just looking for advice on my hypothesis, I can definitely carry out the test.

You'll need specialized equipment to be able to measure the charging time accurate enough to make any conclusions.

 

You'll need specialized equipment to be able to measure the charging time accurate enough to make any conclusions.

I used a resistor that slowed it down enough that there would be little opportunity for human error.
Quite frankly, I just need advice on my hypothesis right now.

 

You are in grade 8. Meanwhile you have about a dozen professionals who have worked with capacitors for all of their lives totaling about 500 years of collective experience on the subject.

You cannot suddenly arrive at a hypothesis if there isn't one.

You can add a resistor to slow down the charge time. That is great. This overrides any ESR for all types of capacitors.
Now you can apply the charge formula I gave you.
Charge time = 6 x R x C seconds

Since R will be the same when testing each capacitor, the only variation in your experiment is the value C of each capacitor.
How are you going to ensure that all the capacitors you test have exactly the same capacitance?

You need to arrive at a completely different hypothesis.

The only reasonable one I can think of at this point is:

The capacitance value increases with temperature.