Electric Potential
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Electric Potential Electric forces are conservative. Work done by an electric force is W=-q o Ed DU=-W
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Electric Potential. Electric forces are conservative. Work done by an electric force is W=- q o Ed D U=-W. Figure 20-1 Change in Electric Potential Energy. Electric Potential. Definition of Electric Potential V. Electric Potential. - PowerPoint PPT Presentation
Transcript of Electric Potential
Electric Potential
Electric forces are conservative.Work done by an electric force is W=-qoEdDU=-W
Figure 20-1Change in Electric Potential Energy
Electric Potential
,
o o
U WVq qJ jouleSIunit volt VC coulomb
D D
Definition of Electric Potential V
Electric Potential
When working with electric potential we measure only changes in electric potential.The zero point can be set arbitrarily.
Figure 20-2Electric Field and Electric Potential
Electric Potential
Electric field and the rate of change of electric potential.
o
o o
q E sWV E sq qVEs
DD D
D
D
Electric Potential
Electric potential of point charges.
electric potential energy for a point charge
oo
kqVr
kqqU q Vr
Solve problems 1-7, 16-19, and 21-24 on pages 672 and 673.
Electric fields around conductorsExcess electric charges move to the surface of a conductor because that is where they are least affected by the internal charges of the material.
Figure 19-18Charge Distribution
on a Conducting Sphere
Electric fields around conductorsWhen electric charges are at rest, the electric field within a conductor is zero. This works even if the conductor has an internal cavity.
Figure 19-19Electric Field Near a Conducting Surface
Electric fields around conductors
Electric field lines enter conductor surfaces at right angles.
Figure 19-21Shielding Works in Only One Direction
Figure 19-20Intense Electric Field Near a Sharp Point
Electric fields around conductors
Electric field lines are more intense near a sharp point.
Charging by induction
Figure 19-22abCharging by Induction
Figure 19-22cdCharging by Induction
Capacitors
A capacitor is a device that has the ability “capacity” to store electric charge and energy.
Capacitors
Capacitance
charge
: :
is defined asQC Q the on the platesV
V electric potential across the platescoulombUnit farad Fvolt
Figure 20-13A Parallel-Plate Capacitor
Capacitors
2
122
1 C =8.85 10 Coulomb's constant 4
o
o
Permitivity of free space
kk N m
Capacitors
Capacitance of a parallel plate capacitor
d= distance between platesA= area of the plates
oACd
Capacitors
A dielectric material is an insulator that increases the capacitance of a capacitor when placed between the plates.Each material has a dielectric constant k not to be confused with k.(p 665)
Figure 20-15The Effect of a Dielectric on the Electric Field of a Capacitor
Capacitors
Capacitance of a parallel plate capacitor filled witha dielectric
d= distance between platesA= area of the plates
dielectric constant
oACd
k
k
Capacitors
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Energy stored in a capacitor
1 12 2 2
QU QV CVC
