PHY 2049: Physics II Tutoring Center is open in room NPB 1215, M-F 12:00AM -4:00PM. It is free. Hopefully all Wiley Plus problems have been solved. Please see me immediately after the class if there is still an issue.

PHY 2049: Physics II About bicycle riding: If some one shows you a trick, it means that, It is possible to do that trick The person who showed you, can do the trick. It does not mean that you can do the trick. Try it a lot of times and you can too.

Electric fields from different geometrical objects. wires Rings and disks Planes Another algorithm Al-Khwarizmi the Persian astronomer and mathematician, wrote a treatise in Arabic in 825 AD, On Calculation with Hindu Numerals, which was translated into Latin in the 12th century as Algoritmi de numero Indorum[1], which title was likely intended to mean "Algoritmi on the numbers of the Indians", where "Algoritmi" was the translator's rendition of the author's name; but people misunderstanding the title treated Algoritmi as a Latin plural and this led to the word "algorithm" (Latin algorithmus) coming to mean "calculation method". The intrusive "h" is most likely due to a false cognate with Greek αριθμος arithmos = "number". (wikipedia: http://en.wikipedia.org/wiki/Algorithm#Etymology

PHY 2049: Physics II Flux and Gauss’ theorem

PHY 2049: Physics II Gaussian (imaginary) surfaces Flux = Φ = ∑ E.dA E.dA for a cube is easy to visualize. Let calculus do it for a sphere or any other shape. Φc = qtotal /εo

S1: Φc = q/ εo S2: Φc = -q/ εo S3: Φc = 0 S4: Φc = 0

For a cylinder with axial field, no contribution to flux from the side walls. From the far top, >0 Near (bottom) , <0

PHY 2049: Physics II No force/field from the charge outside On inside circle E.4πr2=q/εo Coulomb’s law Very outside, E = k 5q/r2 P + + + + + +

PHY 2049: Physics II The electric field in a metal is zero Charge +q on inside surface. Because it is neutral, outside surface must be -q.

PHY 2049: Physics II Electric field is radial. E.A = 0 for the top and bottom surfaces. Sideways: E 2πrh = λh/ε0 E = λ/ 2πrε0

PHY 2049: Physics II Plane 2EA = σA/εo E = σ/2εo

PHY 2049: Physics II E = σ/εo inside

PHY 2049: Physics II Gauss’ theorem Electric fields due to a point charge (Coulomb’s), a wire and a plane. Charge shells don’t act inside. In an insulator with uniformly distributed charge, only charge enclosed contributes to the field.