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### Topic: Teaching Capacitor to Kids - Suggestions? (Read 9233 times)previous topic - next topic

#### pracas

##### Apr 08, 2010, 03:37 pm
I'm planning to have simplified experiments to demonstrate usage of different components. I'm looking for suggestions on how you can explain the usage of capacitor with a simple experiment to kids(10-13yr olds with no exposure to electronics) a very simple experiment with components limited to the following - resistors, diodes, leds, switches, transistors & batteries.

cheers,
Pracas

#### Osgeld

#1
##### Apr 08, 2010, 05:14 pm
charge a large cap with the battery disconnect it then hook it up to a lamp

#### pracas

#2
##### Apr 08, 2010, 05:38 pm
that would require a huge CAP. Any improvisations on it? I dont want to give a huge cap to the kids(if they end up blowing it!)

#### pwillard

#3
##### Apr 08, 2010, 05:53 pmLast Edit: Apr 08, 2010, 05:56 pm by pwillard Reason: 1
Here is how I learned the function of a capacitor.  (in the dark ages)

I think a great way to explain capacitor... and have it mean something...  is to make an oscillator.

Lets say it's a multi-vibrator type oscillator.

- easy to build.
- 4 resistors, 2 capacitors and 2 NPN transistors...
- all basic cheap stuff.

You adjust the frequency of oscillation by changing the values of the capacitors and you can explain that each part "value" has a specific "capacity" for a charge and as that capacity changes... the frequency changes.  Allowing the explanation of the common Resistor/Capacitor charging circuit and the fact that the transistor "fires" when the charge reaches a specific amount.

Much better, but more technical explanation in the wiki.

http://en.wikipedia.org/wiki/Multivibrator

#### Grumpy_Mike

#4
##### Apr 08, 2010, 06:00 pmLast Edit: Apr 08, 2010, 06:01 pm by Grumpy_Mike Reason: 1
Quote
that would require a huge CAP.

No - not with an low current LED and suitable series resistor. you can see the effects with less than 100uF.

The other way is to hook up an arduino to measure the charging and discharging waveforms on a cap and get the curves plotted out in real time by a processing app.

#### keeper63@cox.net

#5
##### Apr 08, 2010, 06:17 pm
I'll probably get flamed for this, but...

I assume that these kids have already been introduced to the history of electronics, and have knowledge of the Leyden jar, correct? Perhaps they have even constructed one? Because otherwise, they will be getting an incomplete education on electronics.

Giving them a capacitor, showing that it can be charged up and discharged does nothing more than show them another "magic black box", the same as likely how they view their computer, their television, their cell phone, the family automobile - indeed, a myriad of devices that they (and most likely their parents) have no concept of the history behind, the people involved, the trials those people went through to develop it; in short, how it all really works in the end, and most importantly, why.

If they're lucky, and don't learn about the history of capacitors (and the science behind them) from you, then at best, the Leyden jar may be mentioned in passing in their history class (perhaps as a quick blurb next to discussion on Franklin's experiments with static electricity), and another mention on charges and insulators in their science classes (though both of these lessons together may be separated in time by a year or two) - and only the real lucky ones will see the connection between everything, and perhaps strive to know more.

I should hope we could do better by our kids educations.

/full disclosure: I am not a parent.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

#### retrolefty

#6
##### Apr 08, 2010, 06:34 pm
Quote
simple experiment to kids(10-13yr olds with no exposure to electronics)

Well maybe trying to relate a capacitor to something they already understand. Perhaps showing it as a spring, that when streached is storing energy from charging and when released, discharges that stored enegy?

Lefty

#### Senso

#7
##### Apr 08, 2010, 08:12 pm
The water analogy is one of the best to explain a capacitor, say this:

A capacitor is like an water thank, when you connect it to a battery(the "water" supply) it will fill up of water, so if you disconnect the battery the capacitor will during a short amount of time still provide electricity("water") to the circuit(a simple resistor plus one led is a good one).
If you parallel two capacitors you will have the double amount of water and if you wire then in series you will have the same amount of water but the hose have the double of the size, it think that with your teaching skills that I dont have you can elaborate this a little bit more

#### westfw

#8
##### Apr 08, 2010, 08:49 pm
Quote
Quote
that would require a huge CAP.

No - not with an low current LED and suitable series resistor. you can see the effects with less than 100uF.

You can see the effect on most electrical appliances that include a "power" LED connected directly to the supply.  Worth pointing out...

I recommend high-voltage caps made from aluminum foil and plexiglass or similar.  Charge them with some sort of electrostatic generator and compare the intensity of the resulting shocks.  It gives a very solid understanding of the principles involved; you can play we size of plates and separation quite easily, and you can SEE and FEEL exactly what is going on.  (SMALL-ish caps, mind you.  A Leyden jar made from a single-serving yogurt container is probably about the maximum size you should deal with; you only want noticeable shocks, not painful ones.)  (or you can compare size of sparks produced on discharge if everyone is all wimpy...)

#### LuciusMare

#9
##### Apr 08, 2010, 10:06 pm
I found a thing in my old physics book, and it included exactly this example, charge and then put a LED to it. It was explained as the "wallets for electricity", which I found easy to understand

#### westfw

#10
##### Apr 09, 2010, 01:32 am
Quote
my old physics book ... included exactly this example, charge and then put a LED to it.

I feel old...

Don't forget the resistor, or this is a good way to demonstrate "how to destroy an LED."

(WITH a resistor you can also demonstrate RC time constants!)

#### Osgeld

#11
##### Apr 09, 2010, 01:38 am
+ without a resistor the cap will discharge silly quick, thus loosing the ohh feature

#### pracas

#12
##### Apr 09, 2010, 03:40 am
Thanks all! as always a great lot of information...

Quote
I found a thing in my old physics book, and it included exactly this example, charge and then put a LED to it.
This is what i think i will do... working on the values now..

Quote
The water analogy is one of the best to explain a capacitor
... Yes i will be using it..

Quote
I'll probably get flamed for this, but...
No mate.. you are welcome to throw in your thoughts.. isn't it a democratic forum?

Well the kids don't have any introduction to electronics(perhaps a bit to electricity) and my objective is to get them interested in the subject by exposing them to it and helping them experiment. I personally believe that if you teach the 'hows' and then go about the 'whys' at a later stage when everybody knows to use then the 'whys' become more relevant.. if not students might end up loosing interest half the way getting to know the 'whys'. I believe this is true here at the forum as well a lot of people first get the leds glowing, and then do projects and learn about the 'whys' as and when they run into problems during the projects.  I would love to hear the others on this. I believe we have a lot of educators around here...

#### Osgeld

#13
##### Apr 09, 2010, 03:46 am
random safety thought, they do make non polarised electrolytic caps

ie http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P1159-ND