Presentation on theme: "Ch 29 : Electric Potential and Electric Potential Energy"— Presentation transcript:
1Ch 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)
2Electric Field and Electric Potential Remember this……..Electric Field involves the idea of Electric Force, where Electric Potential involves the idea of Electric Energy
3Electric 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.
4Ch 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
5Ch 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
6Electric 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.
729.4 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)
8Electric 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