1. Electric Potential Chapter 17

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

3. 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

4. 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.

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

6. 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

7. 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

8. 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

9.  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.

10. 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

11. 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

12. 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 10 -19 J

13. 17-5 Electric Potential Due to Point Charges E=kQ/r 2 V=Ed Combine together then V=kQ/r