Electronic E-Bytes: Capacitor Science

Welcome to a series called Electronic E-Bytes, where we dive into a different topic for 5 minutes every week. This week, we’re focusing on the science behind capacitors.

Energy can be stored in various ways. A battery stores energy in chemicals, while a slingshot stores kinetic energy in the rubber bands. But unlike batteries, or slingshots for that matter, capacitors store energy in an electric field. That stored energy is called an electric potential, and the flow of that potential, or voltage, is called an electric current.

Now, let’s explore the difference between batteries and capacitors.

Battery Science:

Batteries consist of a case, 2 electrodes, and a paste called an electrolyte. Like a diode, the battery’s negative electrode is called an anode, and the positive electrode is called the cathode. The anode and the cathode are made of different materials that give up and hold on to electrons better, respectively. The cutaway above illustrates this well.

The problem with batteries is that they leak sooner than capacitors, and that they also have a higher chance of exploding or starting on fire than capacitors do. They also don’t last as long as some caps do.

Capacitor Science:

Capacitors are designed rather simply, and unlike batteries, do not use chemical reactions to generate energy. Rather, they use 2 plates that can conduct electricity, with a gap in the middle made out of ceramic, plastic, or something else non-conductive. When connected to a power source, like a battery or generator, electrons flow in and out of the cap and store charges on the plates. Both plates generate an equal but opposite charge, or negative or positive. Again, the cutaway above illustrates it well.

A farad is the capacity of a capacitor 😉 to hold a charge at an applied potential of 1V. Larger plates can hold a larger capacitance. Batteries can store much more energy than capacitors, but don’t last as long. Capacitors also can discharge much faster and recharge quickly, like in a camera’s flashbulb, or can power something for a limited time, like a computer after power loss, so the computer can save files and other functions before losing power completely.

Wrap-Up

Capacitors and batteries differ in a few foundational ways, but are alike and perform alike functions in many ways as well. They each have their own uses, and the world would be much different without them. I have not covered electrolytic capacitors in this article, nor have I covered tantalum caps – those are for a future E-Byte. I also simplified the science a little bit to fit it into a 5 minute, easily digestible, E-Byte sized article.

Thank you for reading Electronic E-Bytes: Capacitor Science! For more projects, click here.

The next Electronic E-Byte will come out next Tuesday.