Physics 212 lecture 5: Electric Potential

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Physics 212 lecture 5 Electric Potential

• Electric Potential Energy Difference (?U)
• work to move a charge in an electric field btwn
  two points
• Work Force x distance
• Work electric force x distance moved

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Electric Potential (Voltage) Difference (?V)
work per unit charge to move a charge between two
points Work/charge force/charge x
distance Work/charge electric field x distance
Electric Potential (voltage) work per
unit charge to move a charge between a point and
infinity
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Special Case Electric Potential Difference in a
Uniform Electric Field
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Special Case Electric Potential Difference due
to a Point Charge
Graph of equipotential lines surrounding a point
charge Note lines of equipotential are ? to
electric field at all pts
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Questions for Groups

• Distinguish between electric potential and
  electric potential energy.
• A (-) charge moves in the direction of a uniform
  E field.
• Does the potential energy of the system increase
  or decrease?
• Does the charge move to a position of higher or
  lower potential?
• A uniform electric field is parallel to the
  x-axis. In which direction can it be displaced
  without requiring the addition of external work?

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Example Ch 5 2Ion accelerates through 115V
gaining K7.37x10-17J. Find charge on ion.
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Example Ch 25 13Insulating rod at rest is
released in E field of 100V/m has ?40?C/m and
?0.1kg/m. Find rod speed after 2m.
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Example Ch 25 22Two 2?C pt. charges at 1m
and 1m on x-axis.A) Find V on y-axis at
y0.5m.B) Find ?U for -3 ?C charge brought in
from infinity.