Ch 20 Electric Potential & Electric Potential Energy

CH 20 Electric Potential & Electric Potential Energy Subject

Electric Potential and Electric Potential Energy (Electric Field)

Electric Potential and Electric Potential Energy of Point Charges

Equipotential Surfaces and Electric Field

Relevant Equations

Relationships

Electric Potential W=-q0Ed ΔU= -W •Depends on the sign of a charge as well as its magnitude. ΔV=ΔU/q0 =-W/q0 •S.I .J/C = V Volt •Only CHANGES are measurable in electric potential. •Scalar Quantity 1eV=1.60 x 10-19 K •Connection between Electric Field and Electric Potential E=-ΔV/Δ S •S.I=V/m 1N/C = 1V/m •Electric field depends on "the rate of change of the electric potential with position"

Electric Potential V=kq/r S.I.=V •V is change in potential of infinity to distance r. •Superposition: is the total electric potential due to two or more charges and is equal to the algebraic sum of the potentials due to each charge separately. •Superposition can be calculated by just adding various number, no vector addition is needed.

Electric Potential Energy

U=qV •Decrease in electric potential energy appears as an increase in kinetic energy (speed). •Positive charges accelerate in the direction of decreasing electric potential. •Negative charges accelerate in the direction of increasing electric potential.

Electric Potential Energy U=q0V = kq0q/r S.I= J •Electric potential energy of two charges separated by an infinite distance is 0. •When finding electric potential energy of more than two charges the total electric potential energy is the sum of terms for U=kq1q2/r2 for each pair in the system.

•Closely spaced contours=rapidly changing altitudes. •Widely spaced contours = flat surfaces. •The terms "equipotential surfaces" and "equipotentials" are used to refer to contours. •Equipotential lines cannot intersect. • Electric fields point in the direction of decreasing electric potential. •Electric fields are perpendicular to the equipotential surfaces.

CH 20 Electric Potential & Electric Potential Energy C=Q/V S.I= C/V farad, F Capacitors

Dielectrics

or

Capacitance for Parallel Plate Capacitators C=ε0A/d C=kε0A/d Dielectric constant K E=ε0/k

•Capacitance depends on A(area) and d(separation). •Capacitance does NOT depend on the amont of charge on the plates Q or the potential difference, V, rather the ration of Q and V. •Capacitance is inversely proportional to both potential difference and plate separation.

Dielectrics are insulating materials used to increase capacitance