9.3 - Electric Potential


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9.3 - Electric Potential

  1. 1. 9.3 – Electric Potential
  2. 2. Electric Potential Energy uniform fieldsThe more we move acharge from A towardsB, the more PotentialEnergy it has.The Potential Energywill be equal to thework done: This is just like: Electric Potential Energy Gravitational PE
  3. 3. Electric Potential (V) uniform fields All points in a field have a Potential. It is the energy a coulomb’s worth of charge would have if placed at that point. Field Lines Lines of Equipotential1. What’s the Potential Difference (pd) between: a) A & C? b) B & D?2. If a Charge of +3C is placed at B, how much PE does it have?3. If a charge of +2C is moved from C to B, how much work would be done? What about -2C?4. If a charge of +3C was placed at B and released, what would it do? How much KE would it have at A?
  4. 4. Electric Potential definitionElectric Potential (V) at a point is the amount of work perunit charge needed to take a small positive test charge froma place of zero potential (infinity) to the point.Potential Gradient (V) and Field Strength (E) Uniform Fields: Just like with Gravitational fields the Electric Field Strength is the same as the Potential Gradient for the sort of uniform field you get between two electrodes.
  5. 5. Potential (V) - + + -This image shows theElectric Potential around chargesand draws it as an equipotential surface.It is easy to see what will happen to a positive charge ifit is placed somewhere on this surface.Electric Fields and Charges behave just like Gravitational fields andMasses, the only real difference is that they can attract AND repel.
  6. 6. Equipotential simulationsFor both simulations click in the drop down box and change it toequipotential. Then shoose different scenarios to see the equipotential lines Vector Fields Applet Electrostatics Applet http://www.falstad.com/vector3de/ http://www.falstad.com/emstatic/ CLICK ON THE PICTURES if the links don’t work
  7. 7. Lines of Equipotential (V)GrapheneThe 2010 Nobel prize for Physics wasawarded to Andre Geim and KonstantinNovoselov of the University of Manchester(UK) for their experiments with Graphene. Around graphene atoms there are ‘valleys’ of equipotential that electrons can flow through, giving the material really unusual electrical properties. If the electron is moving along an equipotential it is doing no work. Electrical current with no resistance ? At room temperature? Click on the pictures for more info
  8. 8. Potential due to a point chargeThe Potential at point P is defined as the amount of work perunit charge needed to take a small POSITIVE test chargefrom a place of zero potential (infinity) to P. P has a +ve potential (+V) -W-Q P has a -ve potential (-V)
  9. 9. Potential due to a point charge continuedThe first graph represents the Force as the +ve test charge moves from ∞ to P.The area under the graph is the Work Done and this allows us to use calculusto get the Potential (V) graph and Equation.
  10. 10. Addition of PotentialPotential is a ScalarJust add the potential fromeach charged body to findthe combined potential.Extra clevernessAt P there might be zeropotential but that doesn’t meanthere is zero field.A +ve charge will move to theright if placed at P so theremust still be a field.