Electric Potential Chapter 17

The conservation of energy very useful way to view electrical activity Also a great problem solving tool

17-1 Electric Potential Energy & Potential Difference The electrostatic force, F=kQ 1 Q 2 /r 2, between any two charges is conservative Depends upon position, just like gravitational potential Therefore, the work done to move a charge is equal to the change in potential energy  PE = -W

The change in PE is when a point charge q moves from some point a to another point b, as the negative of the work done by the electric force to move the charge from a to b The work is done by the electric field so W = Fd = qEd PE b -PE a =-qEd In this case the PE is negative and decreases while the KE increases by an equal amount A +q has the greatest PE near the + plate.

Electric Potential & Potential Difference Electric Potential (potential) is the electric potential energy per unit charge

Only the difference in potential is meaningful thus Difference in potential or potential difference between two points, a and b When the electric force does +W on a charge the KE increases and PE decreases The difference in PE, PE b -Pe a, is equal to the negative of the work, W ba

The unit of potential difference is J/C and given a special name of volt in honor of Alessandro Volta who invented the electric battery Potential difference is often referred to as voltage

There must be a reference position as 0 V, just like a reference level of 0 GPE. Earth is usually 0 V or at in infinite distance

 PE ba =q(V b -V a )=qV ba If a charge q moves through a potential difference of V ab, it potential energy changes by an amount of qV ba Energy is the ability to do work, the electric potential difference is also a measure of how much work a given charge can do.

17-2 Relation between Electric Potential and Electric Field W=Fd=qEd W=-qV ba qEd=-qV ba E=-V ba /d Units, V/m or N/C Minus sign tell us that E point in the direction of decreasing potential

17-3 Equipotential Lines All points along the equipotential line will have the same potential Similar to a topographic map showing equal altitude lines. Drawn perpendicular to electric field lines

17-4 The Electron Volt, a Unit of Energy Joule is very large when dealing with energies on the molecular level so the unit of electron volt (eV) is used 1 eV = 1.6 x J

17-5 Electric Potential Due to Point Charges E=kQ/r 2 V=Ed Combine together then V=kQ/r