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CAPACITOR AND DIELECTRICS (Capacitor (Come in different shape & sizes,…
CAPACITOR AND DIELECTRICS
Capacitor
Come in
different shape & sizes
Used in a variety of electric circuits
Is a
device
that can
store charges
Consists of 2 conductors seperated by a small
air gap or insulator
(dielectric)
Circuit Symbol:
Capacitance
, C
Definition:
Charge store per unit potential diffference change
C = Q/V
Unit:
CV^-1 @ Farad (F)
Capacitor with
large capacitance
can
hold more charges
than smaller ones for the
same potential difference applied
across them
Parallel plate
Combination of capacitors
Energy stored in a charged capacitor
Work done in transferring a small amount of charge from the battery to the capacitor.
Charging and discharging of capacitors
Time constant (t)*
: t = RC
Capacitor will take a longer time to charge when :
Resistance (R) higher
Current (I) flowing smaller
Capacitance (C) higher
Dielectric
Effect:
To
increase the capacitance
by a factor of k
k is called dielectric constant - Dimensionless & is greater than 1
Other purposes:
To limit the potential difference
It keeps plate from coming into contact
Allows flexible plates of metallic foil to be rolled into a cylinder , giving the capacitor a more compact size
Definition:
Is
an insulating material
such as rubber , plastic or waxed paper
