1. Capacitors

2. V = Ed E = V/d, with units of volts/meter
A uniform electric field
is an electric field in which the
field strength does not vary. This gives
a constant force on any charge that
exists in the field.
electric potential difference
= work per unit charge
= force x distance per unit charge
= force per unit charge x distance
= electric field strength x distance
V = Ed
E = V/d, with units
of volts/meter

3. made of two conductors separated by an insulator
Capacitor
a device that stores charge
made of two conductors separated by an insulator
The amount of charge that a
capacitor can store depends on:
1. area of conducting surface
2. distance between the conductors
3. type of insulating material
link

4. Capacitance Q = CV C = Q/V the ratio of charge to potential difference
The SI unit of capacitance
is the Farad, F, named in
honor of Michael Faraday.
One Farad of capacitance means that
one Coulomb of charge may be stored
in the capacitor for each Volt of
potential difference applied.

5. In other words, in a series circuit, capacitance adds as reciprocals,
Capacitor Circuits
Series
1. reciprocal of the total capacitance is the sum
of the reciprocals of the separate capacitors
1/CT = 1/C1 + 1/C2 + 1/C
2. charge is the same on each capacitor
QT = Q1 = Q2 = Q3 = ...
3. total potential difference is the sum of each
VT = V1 + V2 + V
In other words, in a series circuit,
capacitance adds as reciprocals,
charge stays the same,
and voltage adds.

6. C, mF V, V Q, mC
E = 12 V C1 12 C1 C3 C2 10 C3 15
CT = C2
VT =
QT =

7. CT = 4.0 mF VT = 12 V QT = 48 mC E = 12 V C1 12 4.0 48 C1 C3 C2 10 4.815
3.2 48
CT = 4.0 mF C2
VT = 12 V
QT = 48 mC

8. Parallel CT = C1 + C2 + C3 + ... QT = Q1 + Q2 + Q3 + ...
1. total capacitance is the sum of each
separate capacitor
CT = C1 + C2 + C
2. total charge is the sum of the charges
on each separate capacitor
QT = Q1 + Q2 + Q
3. potential difference is the same across
each capacitor
VT = V1 = V2 = V3 = ...
In other words, in a parallel circuit,
capacitance and charge add,
but voltage stays the same.

9. C, mF V, V Q, mC
E = 12 V C1 8 C2 10 C1 C3 4 C2
CT = C3
VT =
QT =

10. CT = 22 mF VT = 12 V QT = 264 mC E = 12 V C1 8 12 96 C2 C1 10 12 12048 C2
CT = 22 mF C3
VT = 12 V
QT = 264 mC

11. Capacitors are often used in conjunction
with resistors in simple circuits that are
called RC Circuits.
Click here and here to view computer
simulations of this type circuit.
Explore this link to learn
more about capacitors.