A uniform electric fieldis an electric field in which the

field strength does not vary. This givesa constant forceconstant force on any charge that

exists in the field.

A uniform electric fieldis an electric field in which the

field strength does not vary. This givesa constant forceconstant force on any charge that

exists in the field.

electric potential differenceelectric potential difference

= = workwork per per unit chargeunit charge = = force force xx distance distance per per unit unit chargecharge = = forceforce per per unit chargeunit charge x x distancedistance = = electric field strengthelectric field strength x x distancedistance

V = Ed V = Ed E = V/dE = V/d, with units of volts/metervolts/meter

CapacitorCapacitora device that stores chargea device that stores charge

made of two conductors separated by an insulator

The amount of charge that acapacitor can store depends on:1. area of conducting surface2. distance between the conductors3. type of insulating material

link

Capacitancethe ratio of chargecharge to potential differencepotential difference

C = Q/VC = Q/V Q = CVQ = CV

The SI unit of capacitanceis the FaradFarad, FF, named inhonor of Michael Faraday.

One Farad of capacitance means thatone Coulomb of charge may be stored

in the capacitor for each Volt of potential difference applied.

One Farad of capacitance means thatone Coulomb of charge may be stored

in the capacitor for each Volt of potential difference applied.

Capacitor CircuitsCapacitor CircuitsSeriesSeries

1. reciprocal of the 1. reciprocal of the total capacitancetotal capacitance is the sum is the sum of the reciprocals of the separate capacitorsof the reciprocals of the separate capacitors

1/C1/CTT = 1/C = 1/C11 + 1/C + 1/C22 + 1/C + 1/C33 + ... + ...

2. 2. chargecharge is the same on each capacitor is the same on each capacitor

QQTT = Q = Q11 = Q = Q22 = Q = Q33 = ... = ...

3. 3. total potential differencetotal potential difference is the sum of each is the sum of each

VVTT = V = V11 + V + V22 + V + V33 + ... + ...

In other words, in a series circuit,In other words, in a series circuit,capacitance adds as reciprocals,capacitance adds as reciprocals,

charge stays the same,charge stays the same,and voltage adds.and voltage adds.

CC11

CC22

CC33

EE = 12 V = 12 V

CCTT = =

VVTT = =

QQTT = =

CC11

CC22

CC33

C,C,FF

V,V,VV

Q,Q,CC

12

10

15

CC11

CC22

CC33

EE = 12 V = 12 V

CCTT = 4.0 = 4.0 FF

VVTT = 12 V = 12 V

QQTT = 48 = 48 CC

CC11

CC22

CC33

C,C,FF

V,V,VV

Q,Q,CC

12

10

15

48

48

48

4.0

4.8

3.2

ParallelParallel1. 1. total capacitancetotal capacitance is the sum of is the sum of eacheach separate capacitor separate capacitor CCTT = C = C11 + C + C22 + C + C33 + ... + ...

2. 2. total chargetotal charge is the sum of the charges is the sum of the charges on each separate capacitoron each separate capacitor

QQTT = Q = Q11 + Q + Q22 + Q + Q33 + ... + ...3. 3. potential differencepotential difference is the same is the same across across each capacitoreach capacitorVVTT = V = V11 = V = V22 = V = V33 = ... = ...

In other words, in a parallel In other words, in a parallel circuit, circuit,

capacitance and charge add, capacitance and charge add, but voltage stays the same.but voltage stays the same.

CC33

EE = 12 V = 12 V

CCTT = =

VVTT = =

QQTT = =

CC11

CC22

CC33

C,C,FF

V,V,VV

Q,Q,CC

8

10

4CC22

CC11

CC33

EE = 12 V = 12 V

CCTT = 22 = 22 FF

VVTT = 12 V = 12 V

QQTT = 264 = 264 C C

CC11

CC22

CC33

C,C,FF

V,V,VV

Q,Q,CC

8

10

4CC22

CC11

12

12

12

96

120

48

Capacitors are often used in conjunctionCapacitors are often used in conjunctionwith resistors in simple circuits that arewith resistors in simple circuits that arecalled RC Circuits.called RC Circuits.

Click here and here to view computerClick here and here to view computersimulations of this type circuit.simulations of this type circuit.

Explore this link to learnExplore this link to learnmore about capacitors.more about capacitors.