Summary Notes AQA A-level Physics: Capacitors

Capacitors
1) Made
up
of two
conducting plates separated by a
gap or


dialectric all
a


2) When
(insulating
connected
mater:

and
positive negative change
to
power source,
a




build uniform electric field.
up
on
opposite plates, creating a




C (F cv-] Capacitance
=




potential difference
charge unit
=
-




per




How dielectric
The
a increases
capacitance?
1) dielectric has polar molecules.

2) When a

change is
applied to
a
capacitor,
an electric field is
generated which causes the

molecules ends
to
align themselves (negative are


attracted to the
positively charged plate and vice
versal
3) This creates an electric field to the electric field of the capacitor
opposing
field
The
larger the
permitivity,
the
larger the
opposing
is.


4) This reduces the overall dectric field which reduces the
potential difference so


the increases
capacitance of material
permitivity dialectric constant
a

->
I
(how good allowing
material at

Ex-relative permitivity
is a



c
E
=
3 Gx = x



For air
=

3r =
field lines

1
to
compared
propagate to in a
vacuum)

&permitivity of free
space
8.85x1012



galler:
-I GC, Cz
+ +


3 itot tC3

, stored
Energy
-




as
'Area under the
graph of
charge stored

III)(v
diference
againstpotential across the capacitor.


= zar=ter
=


=