Transcript 16.1 Electric Potential Energy and Electric Potential Difference As

Lecture Outline
Chapter 16
College Physics, 7th Edition
Wilson / Buffa / Lou
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Chapter 16
Electric Potential, Energy,
and NO – Capacitance
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Units of Chapter 16
Electric Potential Energy and Electric Potential
Difference
Equipotential Surfaces and the Electric Field
Capacitance
Dielectrics
Capacitors in Series and in Parallel
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16.1 Electric Potential Energy and
Electric Potential Difference
It takes work to move a charge against an
electric field. Just as with gravity, this work
increases the potential energy of the charge.
© 2010 Pearson Education, Inc.
16.1 Electric Potential Energy and
Electric Potential Difference
Just as with the electric field, it is convenient
to define a quantity that is the electric
potential energy per unit charge. This is called
the electric potential.
Unit of electric potential: the volt, V
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16.1 Electric Potential Energy and
Electric Potential Difference
The potential difference between parallel
plates can be calculated relatively easily:
For a pair of oppositely charged parallel plates,
the positively charged plate is at a higher electric
potential than the negatively charged one by an
amount ΔV.
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16.1 Electric Potential Energy and
Electric Potential Difference
As with potential energy, only changes in
the electric potential can be defined. The
choice of V = 0 is arbitrary.
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16.1 Electric Potential Energy and
Electric Potential Difference
Electric potential
difference of a point
charge – just like
energy, not path
dependent:
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16.1 Electric Potential Energy and
Electric Potential Difference
Whether the electric potential increases or
decreases when towards or away from a point
charge depends on the sign of the charge.
Electric potential increases when moving nearer to
positive charges or farther from negative charges.
Electric potential decreases when moving farther from
positive charges or nearer to negative charges.
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16.1 Electric Potential Energy and
Electric Potential Difference
The electric potential energy of two charges is
the change in electric potential multiplied by
the charge.
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16.1 Electric Potential Energy and
Electric Potential Difference
The additional potential
energy due to a third
charge is the sum of its
potential energies
relative to the first two.
Further charges extend
the sum.
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16.2 Equipotential Surfaces and the
Electric Field
An equipotential surface is
one on which the electric
potential does not vary; it
takes no work to move a
charge along an equipotential
surface.
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16.2 Equipotential Surfaces and the
Electric Field
Equipotentials are
analogous to
contour lines on a
topographic map.
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16.2 Equipotential Surfaces and the
Electric Field
Equipotentials are
always perpendicular
to electric field lines.
This enables you to
draw one if you know
the other.
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16.2 Equipotential Surfaces and the
Electric Field
Here, these
principles have
been used to draw
the electric field
lines and
equipotentials of an
electric dipole.
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16.2 Equipotential Surfaces and the
Electric Field
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16.2 Equipotential Surfaces and the
Electric Field
The electron-volt (eV) is the amount of energy
needed to move an electron through a potential
difference of one volt.
The electron-volt is a unit of energy, not
voltage, and is not an SI standard unit. It is,
however, quite useful when dealing with
energies on the atomic scale.
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Review of Chapter 16
Electric potential difference between two
points is the work done per unit charge in
moving a charge between those two points.
Equipotential surfaces are surfaces on which
the electric potential is constant.
Electric potential for a point charge:
Electric potential energy for a pair of point
charges:
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Review of Chapter 16
Electric potential energy for an array of point
charges:
The electric field is in the direction of
maximum change of the electron potential.
Magnitude:
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Review of Chapter 16
An electron-volt is the energy gained by an
electron accelerating through a potential
difference of one volt.
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