In a way, a capacitor is a little like a battery.
Although they work in completely different ways, capacitors and batteries both store
electrical energy.
If you have read How Batteries Work, then you know that a battery has two terminals.
Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons
on the other terminal.
A capacitor is much simpler than a battery, as it can't produce new electrons, it only
stores them.
In this video, we'll learn exactly what a capacitor is, and how to work it.
Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting
substance, or dielectric.
You can easily make a capacitor from two pieces of aluminum foil and a piece of paper.
It won't be a particularly good capacitor in terms of its storage capacity, but it will
work.
In theory, the dielectric can be any non-conductive substance.
However, for practical applications, specific materials are used that best suit the capacitor's
function.
Mica, ceramic, cellulose, porcelain, Mylar, Teflon, and even air are some of the non-conductive
materials used.
The dielectric dictates what kind of capacitor it is and for what it is best suited.
Depending on the size and type of dielectric, some capacitors are better for high-frequency
uses, while some are better for high voltage applications.
Capacitors can be manufactured to serve any purpose, from the smallest plastic capacitor
in your calculator, to an ultracapacitor that can power a commuter bus.
NASA uses glass capacitors to help wake up the space shuttle's circuitry and help deploy
space probes.
Here are some of the various types of capacitors and how they are used.
• Air.
Often used in radio tuning circuits.
• Mylar.
Most commonly used for timer circuits like clocks, alarms, and counters.
• Glass.
Good for high voltage applications.
• Ceramic.
Used for high-frequency purposes like antennas, X-ray, and MRI machines.
• Supercapacitor.
Powers electric and hybrid cars.
Let’s go, we'll take a closer look at exactly how capacitors work.
Electric current is the flow of electric charge, which is what electrical components harness
to light up, or spin, or do whatever they do.
When current flows into a capacitor, the charges get “stuck” on the plates because they
can’t get past the insulating dielectric.
Electrons – negatively charged particles – are sucked into one of the plates, and
it becomes overall negatively charged.
The large mass of negative charges on one plate pushes away like charges on the other
plate, making it positively charged.
The positive and negative charges on each of these plates attract each other because
that’s what opposite charges do.
But, with the dielectric sitting between them, as much as they want to come together, the
charges will forever be stuck on the plate (until they have somewhere else to go).
The stationary charges on these plates create an electric field, which influences electric
potential energy and voltage.
When charges group together on a capacitor like this, the cap is storing electric energy
just as a battery might store chemical energy.
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