# Electric Potential Electric forces are conservative. Work done by an electric force is W=-q o Ed  U=-W.

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Electric Potential Electric forces are conservative. Work done by an electric force is W=-q o Ed  U=-W

Electric Potential The convention in our text is that the work done on a system is has a negative sign. Unfortunately the college board help sheets use the opposite convention.

Figure 20-1 Change in Electric Potential Energy

Electric Potential Definition of Electric Potential V

Electric Potential When working with electric potential we measure only changes in electric potential.  he zero point can be set arbitrarily.

Figure 20-2 Electric Field and Electric Potential

Electric Potential Electric field and the rate of change of electric potential.

Electric Potential Electric potential of point charges.

Electric potential Equipotentials are surfaces where the electric potential is the same.

Figure 20-6 Equipotentials for a Point Charge

Figure 20-7 Equipotential Surfaces for a Uniform Electrical Field

Figure 20-8 Equipotential Surfaces for Two Point Charges

Solve problems 1-7, 16-19, and 21-24 on pages 672 and 673.

Electric fields around conductors Excess electric charges move to the surface of a conductor because that is where they are least affected by the internal charges of the material.

Figure 19-18 Charge Distribution on a Conducting Sphere

Electric fields around conductors When electric charges are at rest, the electric field within a conductor is zero. This works even if the conductor has an internal cavity.

Figure 19-19 Electric Field Near a Conducting Surface

Electric fields around conductors Electric field lines enter conductor surfaces at right angles.

Figure 19-21 Shielding Works in Only One Direction

Figure 19-20 Intense Electric Field Near a Sharp Point

Electric fields around conductors Electric field lines are more intense near a sharp point.

Charging by induction

Figure 19-22ab Charging by Induction

Figure 19-22cd Charging by Induction

Capacitors A capacitor is a device that has the ability “capacity” to store electric charge and energy.

Capacitors

Figure 20-13 A Parallel-Plate Capacitor

Capacitors

A dielectric material is an insulator that increases the capacitance of a capacitor when placed between the plates. Each material has a dielectric constant  not to be confused with k.(p 665)

Figure 20-15 The Effect of a Dielectric on the Electric Field of a Capacitor

Capacitors

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