CH 21: Electric Potential “Voltage” (Read it once quickly. Read it a second time slowly)

Vocabulary flashcards covering key terms and definitions from CH 21: Electric Potential and Voltage.

Voltage (electric potential difference)

The difference in electric potential between two terminals; the quantity that drives energy transfer; measured in volts (V).

Electric potential (V)

The scalar quantity whose product with charge gives electric potential energy: Uelec = qV; V = Uelec/q; for a uniform electric field, V = EΔx.

Electric potential energy (Uelec)

Energy of a charge due to the electric field; Uelec = qV and, for a uniform field, Uelec = qEΔx.

Gravitational potential energy (Ug)

Energy due to height: Ug = mgh; analogous to electric potential energy and related to work done.

Work (W)

Energy transferred by a force moving a distance: W = FΔx; ΔUelec = W; for gravity W = ΔUg; for electric potential energy W = ΔUelec.

Electric field (E)

Field that exerts force on charges: E = F/q; units N/C; in this chapter, E is often expressed as V/m; points from positive to negative.

Capacitor

Device that stores energy by separating charges, creating a potential difference ΔV; net charge on plates is zero; electric field lines go from + to −.

Potential difference ΔV

Difference in electric potential between two points; ΔV = EΔx (for a uniform E); relates to work by W = qΔV.

Equipotential lines

Contours of equal electric potential; the electric field is perpendicular to these lines and points from high to low potential.

Conductor at electrostatic equilibrium

Inside a conductor, E = 0; there is no change in potential (ΔV = 0) and V is the same everywhere.

Battery

Device that uses chemical reactions to create internal charge separation, producing a potential difference between terminals (about 9 V for some alkaline batteries; different types have different voltages).

Source of Electric Potential

The electric potential is created by the fields from source charge separation and exists even if there is no external charge present.

Uelec = qV

Relation between electric potential energy and electric potential: potential energy equals charge times electric potential.

Conservation of Energy (ΔK = −ΔU)

The change in kinetic energy is the opposite of the change in potential energy; used to analyze motion of charges in an electric field.

Positive charge moving high to low potential

Gains kinetic energy; the electric field points from high V to low V (E and ΔV directions).

Positive charge moving low to high potential

Loses kinetic energy; the electric field points from high V to low V (opposite to motion).

Electric field direction

Electric field points from regions of higher electric potential to lower electric potential (from + to −).

Units of electric potential

Volt (V); 1 V = 1 joule per coulomb (J/C).

Electric field units in this chapter

Volts per meter (V/m); in earlier chapter units were N/C.

Uelec vs qV relationship

Uelec = qV, showing that electric potential energy is the external charge times the potential.