Physis241semiReview

# Physis241semiReview - Lecture 1-1 Coulombs Law Charges with...

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Lecture 1-1 Coulomb’s Law Charges with the same sign repel each other, and charges with opposite signs attract each other. The electrostatic force between two particles is proportional to the amount of electric charge that each possesses and is inversely proportional to the distance between the two squared. 12 2 ˆ qq Fk r r = q 1 q 2 r 1,2 1,2 1,2 r 2 2 9 0 / 10 99 . 8 4 1 C m N k × = = πε where ε 0 is called the permittivity constant. Coulomb constant: 1,2 by 1 on 2

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Lecture 1-2 Electric Field Define electric field , which is independent of the test charge, q 2 , and depends only on position in space: F E q =  2 0 1 ˆ 4 FQ Er qr πε = = Electric Field due to a Point Charge Q
Lecture 1-3 Dynamics of a Charged Mass in Electric Field For -Q<0 in uniform E downward: 2 2 2 2 () 1 , () 2 1 22 y yx y xx F ma Q E QE a a j j E Ej m yt at xt vt x QEx ya v mv = = = = = − ∴= =  = =    2 2 () () xy x QEt vt v v t v m = += + • Oscilloscope • Ink-Jet Printing Oil drop experiment tan y x v v θ= -Q http://canu.ucalgary.ca/map/content/force/elcrmagn/simulate/electric_single_particle/applet.html v y = at = qE/m t v x >>0

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Lecture 1-4 Electric Field from Coulomb’s Law 2 0 1 ˆ 4 i i i i q Er r πε = + + + + + - - - + - - Bunch of Charges dV dq dA dL ρ σ λ = (volume charge) (surface charge) (line charge) Continuous Charge Distribution dq 2 0 1 ˆ 4 dq E r dE r = = ∫∫  P r Summation over discrete charges Integral over continuous charge distribution P i r i q k http://www.falstad.com/vector3de/
Lecture 1-5 Gauss’s Law: Quantitative Statement The net electric flux through any closed surface equals the net charge enclosed by that surface divided by ε 0 . How do we use this equation?? The above equation is TRUE always but it doesn’t look easy to use. BUT - It is very useful in finding E when the physical situation exhibits a lot of SYMMETRY . 0 enclosed E Q E ndA ε = Φ=

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Lecture 1-6 Charges and fields of a conductor In electrostatic equilibrium , free charges inside a conductor do not move. Thus, E = 0 everywhere in the interior of a conductor .
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Physis241semiReview - Lecture 1-1 Coulombs Law Charges with...

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