Presentation on theme: "Ch 29 : Electric Potential and Electric Potential Energy"— Presentation transcript:
1 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)
2 Electric Field and Electric Potential Remember this……..Electric Field involves the idea of Electric Force, where Electric Potential involves the idea of Electric Energy
3 Electric PotentialThe 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.
4 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 objectsIf force is not constant W = ∫Fds
5 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/r2dxU = kq1q2/r = electric potential energy between point chargesU = positive if charges are the same and negative if they are opposites
6 Electric Potential energy between plates (uniform electric field Between plates there is a constant Electric Field E = F/qThe work done in moving a charge between the plates is W = Fd =EqdSo the change in potential energy between the plates is U = qEd where d = the distance between the plates.
7 29.4 Electric PotentialElectric Potential = U/q where q is the “probe” or “sample charge.Electric Potential is also known as Voltage = VThe 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)
8 Electric Potential For a Point Source, V = kq/r Between 2 parallel plates with a uniform electric field E, V = U/q = EdI remember this as Voltage = Ed for parallel plates like a capacitor