Ladyada: Needle-nose pliers …

Adabot: Needle-nose pliers.

Ladyada: Jumper wire …

Adabot: Jumper wire.

Ladyada: Capacitor …

Adabot: Umm … which one is the capacitor again?

Ladyada: Oh - it’s that one on the left …

Adabot: Ah-ha - Got it.

Adabot: Here is your capacitor.

Ladyada: Thanks.

Adabot: Ladyada, what does a capacitor do?

Ladyada: Oh - a capacitor stores electrical energy.

Adabot: But …isn’t that what a battery does?

Ladyada: Well yes - batteries & capacitors both store electrical energy. But aside from that, they’re quite different from one another.

Adabot: Ohhh … but what makes them different?

Ladyada: Batteries *create* their own electricity, and capacitors need to be filled up with electrical energy from an outside source.

Adabot: So a battery makes electricity … and a capacitor stores electricity?

Ladyada: Yup - you got it.

Adabot: Can a capacitor be filled up with electricity from a battery?

Ladyada: Definitely.

Adabot: Cool! … umm … but why would we want to do that?

Ladyada: Hmm - well there’s lots of reasons.

Maybe you should try asking a capacitor - ?

Adabot: Good idea - I’ll go ask Cappy!

Adabot: Hi Cappy - How are you today?

Cappy: Oh-ho hello there, Adabot! I’m doing quite fine, yourself?

Adabot: All my systems are fully operational, but I have a question - what exactly do you do here in this circuit?

Cappy: Oh - good question! Well, in this circuit, I am filtering power.

Adabot: Filtering … power … and how do you do that?

Cappy: Heh, well you see, this circuit is a power supply. We take electrical power in on one side, fix it up & smooth it out, then we send it out the other side.

Cappy: And I’m the part who does the smoothing. When too much electricity is coming in, I store the extra. And when too little electricity is coming in, I empty out my stored electricity to fill in the gaps.

Adabot: Wow - sounds like you’re a pretty *powerful* part around here!

Cappy: Heh - aye, you might say that, kiddo, yes. But capacitors do more than just filter power.

Adabot: Really? What else do they do?

Cappy: Hmm … let’s see …

Cappy: Capacitors store lots of power to help keep photos brightly lit.

Adabot: A camera flash?

Cappy: Precisely!

Cappy: When the power goes out, capacitors can help a computer run for a bit.

Adabot: Backup power?

Cappy: Right again!

Cappy: A capacitor can let low notes play while filtering out the higher ranges.

Adabot: … oh is that … an … audio filter?

Cappy: Correct!!

Cappy: Capacitors can block electron flow while passing along electrical changes.

Adabot: uhhh … I don’t think I know that one …

Cappy: Oh uhh - that *is* kind of a tough one, it’s called “AC coupling” … but umm … don’t worry about it right now!

Adabot: OK!

Cappy: There’s just one more thing you should know - some capacitors can dance!

Adabot: What?!?

Cappy: ah-do-do-do - da - da-do-dee-da

Cappy: Heh - well, I might be the only capacitor who dances … Still - capacitors do a lot of important work inside of circuits by storing & releasing electrical energy.

Adabot: Agreed - but where do you store all that energy? Do you have a backpack or some kind of big pocket?

Cappy: Hah no - I store electrical energy right here in my body!

Adabot: Woah!

Cappy: Inside every capacitor there are two electrically conductive plates separated by a layer of material that doesn’t conduct electricity.

Cappy: Electrical energy is stored in a capacitor when many electrons gather on one plate, attracted to the other plate which has more empty spaces for the electrons to fill.

Adabot: Oh - just like in a battery! The electrons crowd up on one side hoping they can fill in those empty spaces!

Cappy: Indeed. And a capacitor releases electrical energy when those electrons find an easier way to get to those open spaces by going outside of the capacitors body.

Adabot: Thanks, Cappy - capacitors make a lot more sense to me now!

Adabot: Right - see you later Cappy!

Cappy: You’re very welcome, Adabot - glad I could help! Oh that reminds me - I should get back to work at the power supply circuit!

Ladyada: Hey - you’re back! So did Cappy tell you all about capacitors?

Adabot: He sure did - he’s a pretty amazing guy, and capacitors can be used in all sorts of different ways!

Ladyada: That’s true - and they also come in a lot different sizes & colors. Like these …

Adabot: Wow - those are all capacitors?

Ladyada: Yup - lots of different capacitors for lots of different jobs.

Ladyada: From teeny disks to ceramics, film, and electrolytic capacitors. We even have huge super caps.

Ladyada: Let’s try an experiment with this capacitor. This fellow has 10,000 microfarads of capacitance, and can be used up to 6.3 volts. I’m going to measure the voltage on this empty capacitor with my multimeter. Right now we’re at zero volts.

Ladyada: Now I’m going to charge my capacitor with two double-A batteries. AlI we have to do is touch the leads to the capacitor to charge it up to 2.5 volts.
Ladyada: Now we can use the stored energy inside the capacitor to light up an LED.

Adabot: Ladyada, there’s one thing I’d still like to know …

Ladyada: What’s that?

Adabot: Why don’t any of your capacitors dance?

Ladyada: What?

Adabot: You know - “ah-do-do-do - da - da-do-dee-da”

This guide was first published on May 09, 2014. It was last updated on May 09, 2014.

This page (Transcript) was last updated on May 06, 2014.

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