About Capacitors

Biased switches

A biased switch is one containing a spring that returns the actuator to a certain position. The "on-off" notation can be modified by placing parentheses around all positions other than the resting position. For example, an (on)-off-(on) switch can be switched on by moving the actuator in either direction away from the centre, but returns to the central off position when the actuator is released, Above about the Biased switches information content.

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Mercury tilt switch

The mercury switch consists of a drop of mercury inside a glass bulb with 2 contacts. The two contacts pass through the glass, and are connected by the mercury when the bulb is tilted to make the mercury roll on to them, Above about the Mercury tilt switch information content.

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Knife switch

Knife switches are a more or less obsolete type of power switch used in the 1800s. The live (hot) parts of the switch are uncovered and uninsulated, and they are unsuitable for use at shock-risk voltages. Knife switches have a relatively large contact spacing when open, so in the 1800s were often used to control power machinery running at high voltage, a use that can only be considered dangerous, Above about the Knife switch information content.

What is a Capacitor?

A capacitor is a energy storing device made up of two parallel conductive plates separated by an insulating (dielectric) material.  When a voltage is applied across the plates, the electric field in the dielectric displaces electric charges, and thus stores energy.  It is assumed that there are no free charges in the dielectric (at least in the ideal case), and that while they are displaced, they are not free to move around as in a conductor.  The closest analogy in the mechanical world is probably energy stored by a spring.  Dielectrics come in two types, "polar" and "nonpolar".  Molecules where the "center-of-gravity" (as it were) of the negative and positive charges are at the same point are nonpolar.  If this isn´t the case, the molecule is polar.  H 2O, for example, is polar, but H2 is nonpolar.

Crystal

In chemistry, mineralogy, and materials science, a crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions.

Most metals encountered in everyday life are polycrystals. Crystals are often symmetrically intergrown to form crystal twins.

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Filter capacitor

Filter capacitors are any capacitors used for filtering. Filter capacitors are common in electrical and electronic work, and cover a number of applications, such as:

Glitch removal on dc power rails
Radio frequency interference (RFI) removal for signal or power lines entering or leaving equipment
Capacitors used after the reservoir capacitor to further smooth dc power supplies
capacitors used in audio, IF or RF frequency filters (eg low pass, high pass, notch, etc)
arc suppression

Filter capacitor RF work

Plate Ceramic Capacitor are usually favoured due to extremely low inductance and low cost. Where precision is needed, silver mica capacitors offer superior precision and stability. Where manual tunability is required, plastic film trimmers are sometimes used, though it has long been more popular to adjust the inductor to achieve tuning.