PHYS 211 Exam 2, Spring 2002

pT TT Naren a gine tARELAIE AN ONY oF LIBKARY | OF BUIRUT i Physics Department Physics 211 March 11, 2002 Quiz I Time: 1 hour Name? ooo cceec cere Remark: A correct answer without a solution is not counted Given: ke = 1/(4e,) = 9x10° SI Try to do this test in one hour once only. 1. 2. 3. A particle (1 = 50 g, g = 5.0 4C ) is released from rest when it is 50 cm froma second particle (Q = -20 wC ). Determine the magnitude of the initial acceleration of the 50 g. a. 54m/s? bb. 90 m/s? oc. T2 m/s? 65 ns? €. 36 m/s? Fs x 4. A large, flat, non-conducting surface has a uniform charge density o . A small circular hole of radius R has been cut in the middle of the surface, as shown in the figure. Ignore finging of the field lines around all edges, and calculate (using the superposition principle) the electric @ield at point P , a distance z from from the center of the hole along its axis. Pp Solution: i ¢ panera ee AMERICAN UNIVERSITA LIBRARY i 7 off ee ce 5. A long non-conducting cylinder ( radius = 6.0 mn ) has a non-uniform volume charge density given by au? , where a = 6.0 mC/av and r is the distance from the axis of the cylinder. What is the magnitude of the electric field at a point 2.0 sam from the axis? ( The answers are given with two significant figures ) a 14NC b. LONC co. 18 NC d. 2.0N/C e. 54 NC Solution: 6. A song cylindrical shell (radius = 6.0 cm ) has a charge uniformly distributed on its surface. If the magnitude of the electric field at a point 8.0 cm radially outward from the axis of the shell is 85 WC, how much charge is distributed on a 2.0 m length of the charged cylindrical surface? a. 038nC b. 0.76NC C. 019nC d. 0.57NC e. 0.98 nC Solution A proton ( mass = 1.67 x 107’ kg , charge = 1.60 x 107? C) moves from a point A to point B under the influence of an electrostatic force only. At point A the proton moves with a speed of 60 km/s . At point B the speed of the proton is 80 kin/s . Determine the potential difference 3 — Ya. a +15V b. -15V 6. 33 d. 433 Ve. -20V Solution: 8. An isolated conductor of arbitrary shape has a net charge of + 10 uC . Inside the conductor is a cavity within which is a point charge g = + 3.0 uC. What is the charge (a) on the cavity wall and (b) on the outer surface of the conductor? ( Give your solution) . Two particles, each having a mass of 3.0 mg and having equal but opposite charges of magnitude of 6.0 nC, are released simultaneously from rest when they are a very large distance apart: What distance separates the two at the instant when each has a speed of 5.0 2s. a. 43mm b. 8.6mm c. 7.3mm d. 56mm e. 2.2mm an {wena UN(WVERSIT | LIBEARY | OF PEIROE teey ena een cneesaeremistieed Solution; 10. ge of uniform density 12 C/m is distributed along x axis from x = 2.0 m to x = 5.0 m. What is the electric potential (relative to zero at infinity) at the origine (x = 0.0 . m)? a 91V b. 82V ¢ 74V d 99F e LOL Solution: 1]. In the figure, if / — V4, = 22 V, how much energy is the 50 s/* capacitor? a. 0.78 ms b. O58m/ cc. 0.68ms d. 048mJ e. 0.28 mJ 25 ul Solution: a —— 50° 25 ule 12. A 30 gu capacitor is charged to 40 V and then connected across an initially uncharged 20 u* capacitor. What is the final potential difference across the 30 Lu capacitor? . a 15V b. 40V ¢ 18 d. 21P e. 24V Solution: Vt { { | {| VI