Lecture 8

Page 1

Contents Potential energy Electrical potential energy Electrical potential Electron volt


Potential Energy 

For a system of objects, an energy is associated with conservative forces.

When an object moves from one place to another place, the work done by the force on the object depends only on the initial and final points and does not depend on the path taken between the points.

For a conservative force, we define potential energy U.

The difference in potential energy ΔU of the system as the object moves from its initial position i to its final position f is equal to the negative of the work done W by the force as ΔU = Uf – Ui = -W

The electrostatic force is conservative and therefore there is potential energy associated with the configuration (the relative locations of the object) of a system in which electrostatic forces act.


Electric Potential Energy


Electric Potential Energy


Electric Potential


Electric Potential


Electric Potential


Electric Potential This new unit allows us to adopt a more conventional unit for the electric field which we have measured up to now in Newton per coulomb. With two unit conversions, we obtain

ď ˛ N N .m J V E= = = = C C.m C.m m ď ˛ N V E= = C m

Similarly

V=

J N .m = C C

V N = m C


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