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Learn about electric potential energy, fields, equipotential lines, and the principle of superposition in physics. Explore examples to calculate electric field, potential, and differences.
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Electric Potential Physics Department, New York City College of Technology
Electric potential energy Electric potential Electric field Equipotential lines Principle of superposition Key words
Electric potential energy • The electrostatic force is a conservative force • We can thus define electric potential energy PE: , which means that when a point charge q moves from point a to point b, the change in electric potential energy , is the negative of the work done by the electric force to move the charge from a to b. • Since , we have
Electric potential If a positive test charge q has electric potential energy PEa at point a, the electric potential Va at this point is The unit is Volt (V). V doesn’t depend on q. The difference in electric potential between point a and point b is Electric potential and potential difference
Electric potential and electric field • Since and we have , or
Example #1 Calculate the magnitude of the electric field.
Equipotential lines • Equipotential lines or surfaces • An equipotential surface is one on which all points are at the same potential. • An equipotential surface must be perpendicular to the electric field at any point.
Equipotential lines—continued Solid red: electric field lines Dashed green: equipotential lines
Electric potential due to point charges • Potential due to a point charge Q ( with V∞=0) • Potential due to a collection of point charges is all the potentials added as scalars:
Example #2 Determine the potential at a point 0.50m (a) from a +20C point charge, (b) from a -20C point charge. (a) (b)
Example #3 Calculate the electric potential (a) at point A, and (b) at point B.