TAMU PHYS 208 - PHYS208_Exam1spring15-Solutions (6 pages)

Multiple choice questions Exam A Question MCI MC2 MC3 MC4 ExamB VI VI viii a 11 g a g 1 20 marks Two 1 0 cm diameter non conducting spheres have a total charge of 75 0 J lC shared between them and are placed 1 05 m apart The spheres are not connected to each other 0 a If the force each exerts on the other is 11 0 N and is attractive what is the charge on each l j b If the force each exerts on the other is 11 0 N and is repulsive what is the charge on each I J tlz IT 7S o C IF u rr 18 7S 0XIO j C II oN I OS 2 t1 7 fC D a J I a a1h bt andjz u S 7S OX o jJ frrc i 05 f z 75 0 7 S 0 0 11 l x l bS 2 lT B ISJc O 6 g 3 5 10 0 g z 7S 0 10 ZS 2SxIO r I S Jl IO 10 tJnt tj I 90 0 I tYZ IS x It b t H di n a190 i d f uz to S CI JjiC11ce d ah1d lilAPJm L A tr SI 7S f o il 1 t OS flTco 3 X tX J Ul 1 tl a L flr q S X 0 d 2 30x I u 1 I s etUC iJGI O u 3o p C I I 00 x b 1 I 3tflf J b D 9 Ii O t z y 100 0 1 D 3 1 O Y z 12 10 1 C tUtd 2 0 Z I O J 7 7 3 8 If X 0 til 2 112 D M J Jfff co 100 1 If 110 g S J i 10 1i 1 t J f 2 C x 7 73 25 t I 7s oXlo JS 62 v rlJ 1 r C 6 10 s I 8J f t fl C 1 2 20 marks Find the total electric field E as a vector at the origin 0 in the figure as a result ofthe charges QJ and Q2 under the following conditions e JO a The distances are 25cm and the charges are QI 5 0 f C and Q2 10 0 f C j J b The values ore and QJ are the same as in part a but Q2 10 0 lC y 1 e x Nk t Lflf 10 IVIe J lEI 9 IO I N C 31 2 1 x 10 h 1fL I Q 2 if 9 ox D9NmYc r IO OX c rt C J J El t 0 2S m 2 1 2 5 x O ille t I 5 t x 6 t IO DIoItr e 3 20 marks A thin cylindrical shell of radius R 3 0 cm is surrounded by a second concentric cylindrical shell of radius R2 7 0 cm Both cylinders are 7 0 m long and the inner one carries a total charge Q 4 8 lC and the outer one Q2 5 6 lC The charges are uniformly distributed over the respective cylinders For points far from the ends of the cylinders determine the electric field at a radial distance r from the central axis for the following cases a 2 8 cm 7 b 5 0 cm r c 9 0 cm E z C it l Ii a ol b E s OC JK 27T o os m Lf iyltr C 7 OM 1 CO E if fxIO C 27f 6 Dbm X 7 Drtl c 8 x Jl I 2 5 x Ie IDS N f JUJtJAeM c h J 1 Urt iJt c E 9 oC 27f o o9m I r 6 g D t 1 1 7 0 7 1 1 E f tJ lS eo xllr C 277 o CYI fYt J 7 om x E S xID lzCYN nZ I 1 2 3 x D1 AI X Ie p o w I a f Q 01 27T o DvS mJ e j tj IO C l 7 0 116 E f x tTl C 2JI o Og5 1 I oX 7 0 1 x g sx trJZC rtlz i 2 1f lIO V c p Mtr un I h t o htI E 271 O 06 til J Vx tc vr o UO M 2 c J iI tj x crt C 7 0 Co J 7 11 x osN c no cAtVlcY d Mtc burl D e Xf fS x O I 2 CYNM re9Vn J I 4 20 marks A thin rod of length 2L is centered on the x axis as shown in the figure The rod carries a uniformly distributed charge Q Determine the potential Vas a function of y for points along the y axis Let V 0 at infinity L V Ifl Efi0 y f L c x jX lf L 21 1 x 7 TcQ k L Ji 9z k Lf 2 M 1JFfi1 L tffE Q 2L fL Jl L