Ch21 2 1 The solid line has length A and makes an angle with the negative y axis What is the length of the dotted line y A A cos B A sin C A tan D sin A E cos A x A Ch21 2 2 A charge Q is on the y axis at y d What is the magnitude of the E field at position x on the y axis kQ A d x 2 B y Q kQ x 2 d 2 kQ d C x 2 d 2 2 x D kQ x 2 d 2 E None of these E Ch21 2 3 z The integral E dE means E z z x dE x y dE y z z dE x Often from symmetry one can see that one or more of the three component integrals vanishes An infinite line of charge with linear charge density is along the x axis and extends to At the point A shown what can you can about the x and y components of E y A x A Ex 0 Ey 0 C Ex 0 Ey E Ex 0 Ey 0 B Ex 0 Ey 0 D Ex 0 Ey 0 Ch21 2 4 z A circular ring of radius R uniformly charged with total charge Q is in the xy plane centered ur on the origin The electric field dE at position z h on the z axis due to a small piece of the ring with charge dQ is shown What is the magnitude of the field dE kQ A 2 h k dQ C 2 R h2 dE h k dQ B h2 D R k dQ x y dQ R 2 h2 E None of these ur What is dEz the z component of dE A dE sin B dE cos C dE tan What is cos h A 2 R h2 h 1 D cos 2 2 R h B h R 2 h2 E None of these D None of these C h R Ch21 2 5 A circular ring uniformly charged with positive charge Q is in the xy plane centered on the origin as shown On the z axis E E z z Which graph accurately represents the electric field Ez on the z axis z x z B Ez Ez z C y Ez Ez A z D E None of these is an accurate representation of Ez z Ch21 2 6 What the magnitude of the vector i j x y A 1 B 2 C 0 D Some other number is not a vector E No answer because x y Ch21 2 7 There are no charges near inside the regions shown Which of the following are possible electric field line configurations b a c A a only B b only C c only D None are possible E Some other answer all a and b only etc Ch21 2 8 Consider the four electric field line patterns shown Assume that that are no charges in the regions shown Which if any of the patterns represent possible electrostatic fields I II III IV A All are possible D None are possible B II only C II and III only E None of the above Ch21 2 9 From the figure what can you say about the magnitude of the charge on the bar Q bar compared to the magnitude of the charge Q of the positive point charge A Q bar Q B Q bar Q C Q bar Q Q Qbar From the figure what can you say about the net charge on the bar A Qbar 0 B Qbar 0 that is the bar has a net positive charge C Qbar 0 the bar has a net negative charge D Not enough information in the figure to answer the question Ch26 10 Two infinite planes are uniformly charged with the same charge per area If one plane only were present the field due to the one plane would be E B A The field in region B has magnitude A zero B E C 2E D depends on exact position C The field in region A has magnitude A zero B E C 2E D depends on exact position Ch21 2 11 A dipole is placed in an external field as shown In which situation s is the net force on the dipole zero 1 3 A B C D E 1 2 1 and 2 3 and 4 2 and 4 2 4 Ch21 2 12 velocity V t 4m s 4m s time t 0 5 10 15 For 1D motion if velocity v is constant then the displacement in time t is d v t If v is not constant then the displacement is z tf d v t dt The graph above shows v t ti What is the displacement after 10 seconds A 3m D 18m B 8m C 10m E None of these Ch21 2 13 Areal mass density of a tile is mass m per area A m A If a sheet has area A and uniform density then its mass is m A If a sheet has a non uniform density x y where x y is the postion on the sheet then the total mass of the sheet is bg m z da z d2r zzb g x y dx dy where da d2r represents an infinitesimal area element Consider a square sheet in the x y plane with edge length L and density b kx where b and k are constants Which expression below correctly represent the integral for the mass y L da s L L Green L b kx dx L 2 Yellow L 0 0 L Pink kx dx b kx dx L Blue 0 Purple None of these don t know b kx dx 0 x
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