6.1 Capacitors
, Capacitors
Electrical component in which
charge is stored A .
capacitor consists of
two charged plates separated from each other
equally by an insulator
(dielectric) such as air ,
paper ,
ceramic or mica .
+
_
> >
direction of
^ v flow of
+ Q -
Q
electrons
-
+
-
+
' <
± =
A B
•
when the capacitor is connected to the cell , electrons flow from the cell for a short period
of time .
•
Electrons cannot travel between the plates because of the insulation The current .
causes
electrons to be removed from plate A.
making it
positively charged . Plate B gains
electrons , aqui ring a negative charge .
•
The two plates have
charge that is equal in
magnitude but opposite in charge as
the circuit 's current must be equal in all places and charge must be conserved .
Therefore there is potential difference across the plates
•
a .
•
When the p d.
-
across the plates is equal to the e.m.fi of the cell the current , falls
to zero
the capacitance of a capacitor is defined as the charge stored per unit potential
difference across the capacitor :
C = Q Q = VC
capacitance C , ,
in farads ,
F
charge stored ,
Q in coulombs C
, ,
potential difference V. ,
in volts V ,
charge on the capacitor a
potential difference across the capacitor
, Capacitors
Electrical component in which
charge is stored A .
capacitor consists of
two charged plates separated from each other
equally by an insulator
(dielectric) such as air ,
paper ,
ceramic or mica .
+
_
> >
direction of
^ v flow of
+ Q -
Q
electrons
-
+
-
+
' <
± =
A B
•
when the capacitor is connected to the cell , electrons flow from the cell for a short period
of time .
•
Electrons cannot travel between the plates because of the insulation The current .
causes
electrons to be removed from plate A.
making it
positively charged . Plate B gains
electrons , aqui ring a negative charge .
•
The two plates have
charge that is equal in
magnitude but opposite in charge as
the circuit 's current must be equal in all places and charge must be conserved .
Therefore there is potential difference across the plates
•
a .
•
When the p d.
-
across the plates is equal to the e.m.fi of the cell the current , falls
to zero
the capacitance of a capacitor is defined as the charge stored per unit potential
difference across the capacitor :
C = Q Q = VC
capacitance C , ,
in farads ,
F
charge stored ,
Q in coulombs C
, ,
potential difference V. ,
in volts V ,
charge on the capacitor a
potential difference across the capacitor
