# What is a capacitor? [video]

Iām not watching unless he explains the flux capacitorā¦

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I think I had the hardest time figuring out transistors initially ā one of the biggest things that helped me was this site, which includes important clarifications like:

Current does not flow. Electric current never flows, since an electric current is not a stuff.

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I find that to be a very misleading explanation of how a BJT works. A BJT is certainly a current controlled device, accordingly current is simply created by voltage and resistance, but it is a important distinction. You can not simply wire a battery directly into the base of a transistor and not have it cause problems (at least not usually) - this is something that can be done with the gate on a MOSFET (since it is a voltage controlled device).

For the simple ON/OFF explanation it works well enough (simplifying it to the level of a two step diode), but even they say:

Just by coincidence, the tiny base/emitter current is proportional to the large collector/emitter current. The transistor ACTS as if it is amplifying current. But itās really using a small change in voltage to create a large change in current.

Ironically that small change in voltage causes a small change in the input current, which in the vast majority of circuits will show a resistor (or some type of input resistance) that causes this voltage/current relationship. When trying to pin point input bias currents for a BJT output stage of an audio amplifier one does not look to the spec sheets for voltages, they would be presented in terms of current. You would then use that, along with the voltage that your amplifier is running off of to calculate the amount of input resistance to give you the needed bias current.

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If Make does a video on an Inductor and says it stores energy/charge/electricity so help me I will never take them seriously again, ever.

A person at my work once gave a presentation about semiconductors but the only thing I could remember later was that a diode is like a stop light on a one way street. I need very simple metaphors like that to understand electronic circuitry. Making a wafer is essentially magic as far as I can tell.

This video has the same problem that I have with nearly every āintroductoryā electoronics explanation that covers capacitors - how are they used?

Great, I can charge it. But either 1) it has to discharge in bursts, or 2) my input power is stronger than the rate that Iām discharging the capacitor. So what good is it? When would I use it?

Someone who doesnāt really understand electronics well can sort of understand how a diode is used, or how a resistor is used, how electricity flows conceptually, etc. But never seem to get what the applications for a capacitor are versus, well, a constant power source.

Iām not asking the question, just wish these things would take that extra step for beginners.

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Yep. It left much unanswered and unspecified.
As far as I could tell, by the video, a capacitor is like a rechargeable battery. Why do so many electronic devices need several ārechargeable batteriesā in them as well as an outside power source?

You mean like if you string 8 of these and let each of them represent 0 or 1 depending on whenever itās fully charged or fully discharged? Thus you got 8 bit RAM. And then you build and shrink this design a million timesā¦which is what your common RAM is. Except, you donāt see every single capacitor because itās too small and underneath the plastic covering of the chipā¦

Or if you more analog, instead of discrete designs, how about filtering? Ever use a mic.? Or regulate power?

Of course more educated and knowledgeable people would probably cringe at my over simplification of design, but hey practical electronics. Not physics.

Why is he wearing lipstick?

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