PHYS 211 Exam 2, Spring 2001

‘ ‘s 6 , : _ {Tena te piate | : : ra AMERICAN CNTVER . , . . | Here | . ” mt. ee - -—— . . Physics Depariment Physics 211 Date: 1 14, 2001 AUB Quiz I Tingé: I hour Name: tama “Trev onsion, ILD. No.: Qool edo Sy Encircle your section Section 1. 9M J. Katul Section 2. 9M B. Bodakian Section 3. 9Tu J. Katul SectionG,) 9Tu _B. Bodakian Show your solution and encircle the correct answer given. A correct answer without solution is not counted Useful Information k= —! =9x10° MKSA Are c e=16x loc 10 marks 1. Identical point charges Q are placed at each of the four corners ofa 3.0m x 4.0m rectangle. IfQ= 40 wC, what is the magnitude of the electrostatic force on any one of the charges? © a. 3.0N Ous c. 1.8N Solution: e aq = “> => Eas Es aty 3 = Fant EaneEun: re) Bolo NL j ay E2y+ Euys £ Fay: LSEke Me Eq = Vig ebay? - S93 S64 VE \Fl- Qq. _ no use € 2 ‘ Saasee 2 2,396 10 marks 2. IfQ= 80nC, a= 3.0m, and b= 4.0m in the figure, what is the magnitude of the electric field at point P? a. 45 N/C b. 70 N/C c. 29N/C Cu N/C e.92N/C Solution: E, 10 marks 3. Charge is uniformly distributed along the entire x axis. If each 20-cm length of the x axis carries 2.0 nC of charge, what is the magnitude of the electric field at the point, y = 2.0 m, on the y-axis? a a 45NIC () 90NIC d.36N/C e. 18079c“\ i | via Solution: ay ks anngec : Charge of uniform density (80 nC/m? ) is distributed throughout a hollow cylindrical region formed by two coaxial cylindrical surfaces of radii, 1.9 mm and"3.0 mm. Determine the magnitude of the electric field at a point which is 2.0 mm ‘from the symmetry axis. a. 7.9 NIC (v)o0 N/C @ponic {9 6.8N/C ©. IS N/C Solution : 10 marks 5. Three identical point charges (+2.0 nC) are placed at the corners of an equilateral triangle with sides of 2.0-m length. If the electric potential is taken to be zero at infinity, what is the potential at the midpoint of any one of the sides of the triangle? al6V b. 10 V c. 70V (Gas v e.44V Solution: 10 marks 6. Two identical particles, each with a mass of 4.5 mg and a charge of 30 nC, are moving directly toward each other with equal speeds of 4.0 m/s at an instant when the distance separating the two is equal to 25 cm. . What minimum separation distance will the two achieve? Gee a. 98cm b, 12cm Kis cm d.15cm Solution: each park< co is Suloyte ac he an _, Hlecbnostatve mer Bo 10 marks 7. Inthe figure, if C, =20 uF, Cy =10 pF, C3= 14 pF, C4 = 30 pF, and V,= 45 V, determine the charge stored by C4. a. 0.250 mC b. 0.28 mC c. 0.300mC d. 300mC e.(9)360 mC Solution: Ce 2h yl 10 marks 8. What total energy is stored in the group of capacitors shown if the potential difference V.. is equal to 50 V ? Solution: a. 48 mJ b. 27 mJ c. 37 mJ £@i9 ml e. 10 mJ a 10 marks 9. A capacitor has square plates, each of side a, making a small angle with each other as shown in the figure. Find the capacitance. é,@ a 20s 22 4 Se bc += ° d aay) 2 ab : -—) e. none of the above my answer is : wse=s atrocyg Ec: &! = Lo. a 10 marks 10, Consider two widely separated conducting spheres, ] and 2, the second having twice the diameter of the first. The smaller sphere initially has a positive charge g and the larger one is initially uncharged. You connect the spheres with a long thin wire. The final charges g,and q, on the spheres in term of q are: =f 2q a+ 39 =424 a 3° 2 3 b. Hara URts oh Hts =~Q2AR d.g, =+ a > 4 e) none of the above, my answer is: () = \ Re. Az