A paper or plastic capacitors has metal foil
strip as their conductor plates.
plate thereby providing a thin insulating
layer between the plates. The thinner the
layer, the higher the capacitance.
Note that: Electrolytic capacitors are
connected with great care. Their ends are
labelled positive or negative as safety
precautions because a wrong connection can
lead to an explosion.
The insulating materials are rolled up and
sealed inside a metal box so as to prevent
moisture from entering.
Air filled capacitor
This is the capacitor in which the insulating
(dielectric) material is air.
Mica capacitor
The capacitance of such capacitor is altered
by changing the overlapping area between
the plates.
This is the capacitor in which the sheets of
metal foil are separated by strips of mica as
dielectric material.
Note that, air filled capacitor is an example
of variable capacitor which are mainly used
for tuning radios.
Variable capacitor is the one whose
capacitance can be varied. Fixed capacitor is
the one whose capacitance cannot be
changed
Mica is preferred because it is a natural
mineral and splits easily into very thin
sheets.
CHARGING A CAPACITOR
Charging a capacitor is the process of
increasing the potential difference across a
capacitor’s plates by connecting it to a
power supply with a higher voltage.
Electrolytic capacitor
This is the capacitor in which the metal
sheets are separated by a paper soaked in a
chemical compound. The soaked paper is
not an insulating material.
A capacitor is charged by connecting its
plates with the terminals of a cell. In this
way the current flows in the plates.
Action
As the capacitor charges, a thin layer of
aluminium oxide are formed on the positive
