How to Build a Capacitor

Last Updated: October 6, 2021

Capacitors range from a simple, low-voltage setup to complex high-voltage machinery. If you just want to try your hand at making a simple capactior, our how-to guide will show you how!

Steps

1
Fill a non-metallic vessel (such as a paper cup, or a plastic bottle) with warm saltwater. Use warm water to dissolve the salt.
2
Wrap the outside of the vessel with aluminum foil, or tin foil.

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3
Place a metal object (such as a knife, a nail, etc) in the saltwater. The foil is one terminal, and the water/metal object combination is the other. Do not allow the water or the metal object to touch the foil or spill over the side. This will short the capacitor and make it impossible to charge.
- Later you can use a voltmeter to verify if the capacitor can hold a charge.
4
Charge it up, by applying the voltage from an ordinary household battery, to both terminals. After a few seconds disconnect the battery and connect the voltmeter to the terminals of the capacitor. Any reading (mV-V) will indicate a charge.
5
Congratulations, you have a working capacitor, capable of holding an electric charge!

Community Q&A

Question

What is the advantage of a salt water capacitor over a water capacitor?

Community Answer

Salt water is more conductive than plain water, so it will hold a charge better.
Question

Does the capacitor have any specific polarity?

Community Answer

Some do. Electrolytic capacitors have the polarity marked. Hooked up backward, they pop and let the magic smoke out. Other types are not polarity sensitive.
Question

Do I need to wrap the bottom of the capacitor?

Community Answer

Not necessarily. The capacitive effect occurs from the separation of the two plates (conductors). Not wrapping the bottom reduces the size of the plates (conductors), resulting in less capacitance, or a less capacitive effect, so you just have a smaller capacitor vs. the overall physical size of the unit that could have been utilized to maximize its energy potential.

Warnings

Capacitors are very dangerous. Do not touch one after it has been charged by a power source, because it will shock you.

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