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Unformatted text preview: ins or loses when a charge of magnitude e (an electron or a proton) is moved through a potential difference of 1 volt 1 eV = 1.60 x 10-19 J Units Potential Difference in a Uniform Field
• The equations for electric potential can be simplified if the electric field is uniform: • The negative sign indicates that the electric potential at B is lower than at point A Energy and the Direction of Electric Field
• When the electric field is directed downward, point B is at a lower potential than point A • When a positive test charge moves from A to B, the charge-field system loses potential energy Electrical Potential Energy h d Gravitational Potential Energy Work = Fd = mgh G.P.E. = mgh Electrical Potential Energy Work = Fd = qEd E.P.E. = qEd Equipotentials
• Point B is at a lower potential than point A • Points B and C are at the same potential • The name equipotential surface is given to any surface consisting of a continuous distribution of points having the same electric potential Charged Particle in a Uniform Field, Example
• A positive charge is released from rest and moves in the direction of the electric field The change in potential is negative The change in potential energy is negative The force and acceleration are in the direction of the field • • • Potential and Point Charges
• A positive point charge produces a field directed radially outward • The potential difference between points A and B will be Potential and Point Charges, cont
• The electric potential is independent of the path between points A and B • It is customary to choose a reference potential of V = 0 at rA = • Then the potential at some point r is • Multiple charges Potential Energy of Multiple Charges
• Consider two charged particles • The potential energy of the system is •If there are more than two charges, then find U for each pair of charges and...
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- Winter '10