# Ch 29 : Electric Potential and Electric Potential Energy

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Ch 29 : Electric Potential and Electric Potential Energy
Ch 29 defines electric potential (Voltage) and potential energy (these are 2 different terms and mean different things)

Electric Field and Electric Potential
Remember this…….. Electric Field involves the idea of Electric Force, where Electric Potential involves the idea of Electric Energy

Electric Potential The electric field allows us to understand something about electricity by looking at electric forces and how a charge exerts a force on another charge. The electric potential is looking at electricity in terms of energy. The analogy is looking at Newtonian mechanics in terms of Forces or in terms of energy.

Ch 29.1 Electric Potential Energy Connection with mechanical energy
Change in U = -work done by a conservative force. Ugrav = mgh = potential energy of a system of objects If force is not constant W = ∫Fds

Ch 29.2 Potential energy of point charges
Using the idea that the work done equals the negative change in potential energy, can derive the change in U between 2 point charges. U = -W = ∫Fdx = ∫kq1q2/r2dx U = kq1q2/r = electric potential energy between point charges U = positive if charges are the same and negative if they are opposites

Electric Potential energy between plates (uniform electric field
Between plates there is a constant Electric Field E = F/q The work done in moving a charge between the plates is W = Fd =Eqd So the change in potential energy between the plates is U = qEd where d = the distance between the plates.

29.4 Electric Potential Electric Potential = U/q where q is the “probe” or “sample charge. Electric Potential is also known as Voltage = V The electric potential depends only on the sources charge(s) and their geometry much like Electric Field only depends on the source charge. U = qV (commonly used equation for finding potential energy if you know the Voltage or electric Potential)

Electric Potential For a Point Source, V = kq/r
Between 2 parallel plates with a uniform electric field E, V = U/q = Ed I remember this as Voltage = Ed for parallel plates like a capacitor