7-10-2015 FCI 1

Chapter 1 L2: Electric potential,

Potential difference in uniform electric field.

Electric potential point charge.

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Electric Potential EnergyElectrical potential energy is the energy

contained in a configuration of charges. Like all potential energies, when it goes up the configuration is less stable; when it goes down, the configuration is more stable.

The unit is the Joule.

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Potential difference and electric potentialThe potential difference ∆V = VB - VA between

two points A and B in an electric field is defined as the change in potential energy of the system when a test charge is moved between the points divided by the test charge qo:

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The electric potential is a measure of potential energy per unit charge, the SI unit of both electric potential and potential difference is joules per coulomb, which is defined as a volt (V)

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that the SI unit of electric field (N/C) can also be expressed in volts per meter:

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7-10-2015 FCI 10

Electric Field and Electric Potential

E = - V / dTwo things about E and V: The electric field points in the direction of

decreasing electric potential.The electric field is always perpendicular to

the equipotential surface.

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7-10-2015 FCI 12

Sample ProblemDraw field lines for the charge configuration below. The field is 600

V/m, and the plates are 2 m apart. Label each plate with its proper potential, and draw and label 3 equipotential surfaces between the plates. You may ignore edge effects.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

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