Electronics Stuff, Enter PLEEEASE if you know about Capacitors!!?

Question

I have an assignment to hand in later this week!!!

Could somebody please explain "The construction of a simple parallel plate capacitor"

And briefly explain how a variable capacitor works?

Answer 1

A capacitor is two conductors seperated by an insulator (also called a dielectric). A simple parallel plate capacitor can be seen in older radios, attached to the tuning knob. The aluminum plates are the conductors, the air between the plates is the dielectric. The capacitance varies as the plates mesh with one another. The greater the surface area of the plates, the greater the capacitance.[Also. The closer the plates the greater the capacity to store charge (capacitance). If the plates touch, there is no capacitance.]
Modern caps are foils of conductive material with a thin dielectric in between (think of a sandwich) then rolled up to save space.

Answer 2

Basically, capacitors are storage mechanisms that alternate plates of conductive material (like copper) with a non-conductive dieletric (like air or paper). See wikipedia.org for a more in depth answer:

Capacitors:
http://en.wikipedia.org/wiki/Capacitor


Variable capacitors use two sets of movable plates to vary the amount of area between the plates. Again, see wikipedia.org
Variable Capacitors.
http://en.wikipedia.org/wiki/Variable_capacitor