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Electric Potential. Gravitational Potential. gravitational potential energy (work) per unit of mass. high PE. low PE. + + + + + +. - - - - - -. q. +. gain in KE = loss of PE. PE depends on charge q. Electric potential = potential energy (work) per unit of charge.
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Gravitational Potential gravitational potential energy (work) per unit of mass
high PE low PE + + + + + + - - - - - - q + gain in KE = loss of PE PE depends on charge q
Electric potential = potential energy (work) per unit of charge V = UE/q = volts J/C units: only differences of potential (voltages) are measurable
If define V = 0 @ infinity, then can designate V at a point Work to move a charge (q) from infinity (a great distance) to a given point: W = UE = qV
5000 V - - - + + + e- electron accelerated through 5000 V -8.01 x 10-16 J ΔPE: speed: 4.20 x 107 m/s
Energy Units S.I. unit: Joule UE = qV 1 J = (1 C) ( 1 V) electron volt (eV): charge of 1 e- across a potential difference of 1 V 1 eV = (1 e-) (1 V)
1 eV = (1.602 x 10-19 C) (1 V) = 1.602 x 10-19 J 5000 V - - - + + + 2e- energy = 10 000 eV
Q KE: QV - - - + + + m v: √(2QV/m) V 2Q KE: 2QV 2m v: √(2QV/m)
Uniform Electric Field Field strength (+force) is constant
Relationship between V and E for a Uniform Electric Field (between charged plates) W = Fd F = Eq qV W = UE = E = V/d qV = Eqd V/m units: N/C =
E = V/d V = V2 – V1 V2 L ·P r V1 Electric field @ P? Electric potential @ P?
Electric Potential around a Point Charge +Q r X V = kQ/r UE = Vq = kQq/r
If more than 1 point charge: find V for each (include sign) and then find algebraic sum V = k Σi (qi/ri)