Q a v 4 r 3 3 qb a 4r 2 28 3 4 q a 3 r 1 r 2 qb

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Unformatted text preview: it calculated?” • Linear (λ=Q/L) Coulombs/meter • Surface (σ = Q/A) Coulombs/meter2 • Volume (ρ = Q/ V) Coulombs/meter3 Some Geometry Asphere = 4πR 2 Acylinder = 2πRL Vsphere = 4 πR 3 Vcylinder = πR 2 L 3 What has more net charge?. A) A sphere w/ radius 2 meters and volume charge density ρ = 2 C/m3 B) A sphere w/ radius 2 meters and surface charge density σ = 2 C/m2 C) Both A) and B) have the same net charge. Q A = ρ V = ρ 4 πR 3 3 QB = σA = σ 4πR 2 28 3 4 Q A ρ 3 πR 1ρ = = R 2 QB σ 4πR 3σ Physics 212 Lecture 2, Slide 14 Physics 212 Lecture 2, Slide Checkpoint 4 Two infinite lines of charge are shown below. Both lines have identical charge densities +λ C/m. Point A is equidistant from both lines and Point B is located above the top line as shown. How does EA, the magnitude of the electric field at point A compare to EB, the magnitude of the electric field at point B? A. EA < EB B. EA = EB C. EA > EB “Since A is located in between two equally charged Since lines, the electric field in between cancels to 0 at A's location. In contrast, point B feels the electric field from the top line pushing upward as well as some of the electric field from the bottom line pointing in the same direction.” 29 Physics 212 Lecture 2, Slide 15 Physics 212 Lecture 2, Slide Calculation “I really think it would be nice to go over how to really find the electric field with the infinite lines of charge with the integrals” charge y P r C h a rg e is unifo rm ly d is trib ute d a lo ng th e x­a xis fro m th e o rig in to x = a . T h e c h a rg e d e nis ty is λ C /m . Wh a t is th e x­ c o m p o ne n t o f th e e le c tric fie ld a t p o int P : (x,y) = (a ,h ) ? h dq=λdx x x a We kno w: dq ˆ E = ∫k 2 r r dq Wh a t is ? r2 (A) 33...
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This note was uploaded on 04/14/2013 for the course PHYS 212 taught by Professor Selen during the Spring '08 term at University of Illinois at Urbana–Champaign.

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