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Electric Potential

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

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Electric Potential

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  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=kQ1Q2/r2, 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 • PEb-PEa=-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, PEb-Pea, is equal to the negative of the work, Wba

  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. PEba=q(Vb-Va)=qVba • If a charge q moves through a potential difference of Vab, it potential energy changes by an amount of qVba • 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=-qVba • qEd=-qVba • E=-Vba/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/r2 • V=Ed • Combine together then • V=kQ/r

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