A uniform electric field, with a magnitude of 600 N/C, is directed parallel to the positive x-axis. If the potential at x = 3.0 m is 1 000 V, what is the potential at x = 1.0 m? b. 1 600 V c. 2 200 V d. 2 500 V a. 400 V PHY 2049: Physics II Coulomb’s law, electric field, Gauss’ theorem and electric potential. -W = qΔV Energy conservation applies. U F V E

PHY 2049: Class Quiz If 500 J of work are required to carry a charged particle between two points with a potential difference of 20V, the magnitude of the charge on the particle is: A. 0.040C B. 12.5C C. 20C D. cannot be computed unless the path is given E. none of these E=25C

PHY 2049: Physics II What is the potential at the center point (in units of kq/d) ? a) -7 (b) -5 (c) -7 (d) -7

PHY 2049: Physics II Calculate the Electric Field at P Calculate the el. potential at P

PHY 2049: Physics II Point charge Distribution of charges Line charge at an edge Disc on an axis through the center

Some old business: What is the electric field of a shell of a uniform spherical charge distribution? What is the potential for each of the above?

PHY 2049: Physics II Some old business The potential of a uniform spherical charge. Calculate electric field, integrate it to get the potential E r R V V

Two particles with charges Q and -Q are fixed at the vertices of an equilateral triangle with sides of length a. The work required to move a particle with charge q from the other vertex to the center of the line joining the fixed particles is: A. 0 B. kQq/a C. kQq/a2 D. 2kQq/a E. 1.4kQq/a a

PHY 2049: Physics II a= 39 cm q1 = 3.4pC q2 = 6 pC E at the center? What is the potential at the center? Keep in mind that electric field is a derivative and one needs V(x,y,z) and not just V(0,0,0) at the center.

PHY 2049: Physics II An outline Capacitors, plate, coaxial, spherical.. Energy, Dielectric strength, Dielectric constant. Netweorks: Parallel and Series configuration.

PHY 2049: Physics II Capacitors: A device to hold charge. It is held by Coulomb force between the charges. +q and –q on two separate places. V : potential difference: q= CV C: capacitance units farad.

PHY 2049: Physics II

PHY 2049: Physics II

Potential near a sheet charge

Potential near a sheet charge

PHY 2049: Physics II

PHY 2049: Physics II What about the

PHY 2049: Physics II

HITT A uniform electric field, with a magnitude of 600 N/C, is directed parallel to the positive x-axis. If the potential at x = 3.0 m is 1000 V, what is the potential at x = 1.0 m?   a. 400 V b. 1600 V c. 2200 V d. 2500 V c

PHY 2049: Physics II What is the capacitance of various familiar balls. C = 4πεoR = 10-10 R(m) F Basketball-it is an insulator Van de Graff top Earth (radius 6.4 X 106 m) CE = 0.71 mF

PHY 2049: Physics II Energy stored in a capacitor U = ½ CV2 = Q2/2C = ½ QV Dielectric Strength (oops I burned it/broke it) Capacitor Enhancement by inserting a dielectric: Replace εo by κεo

PHY 2049: Physics II

PHY 2049: Physics II Ceq = C1+C2+C3

PHY 2049: Physics II

PHY 2049: Physics II Charging and discharging of capacitors. http://edugen.wiley.com/edugen/instructor/main.uni

PHY 2049: Physics II 25.20

PHY 2049: Physics II Switch closed on left, capacitor C1 is being charged We have C2 = C3 = 20 μF in parallel. The equivalent capacitor is then Ceq = 40 μF. When the switch is thrown to right, the battery is disconnected, the charge is shared between the capacitors C1 and Ceq = 40. What is the charge on old C2 and C3? Is your answer 40 μC? What is your answer if C2 = 10 μF and C3 = 30 μF?

PHY 2049: Physics II All about capacitors Capacitance units Farad C = 4 π κεo R for a sphere of radius R and dielectric constant κ. Energy stored dielectrics and strength Parallel and series elements in a network