PHY 2054 Exam 1 Spring 2011 Key Solution

PHY 2054 Exam 1 - Reitze/Kumar PHY2054 Exam 1 Useful Constants ke= 8.99109 Nm2/C2 0= 8.8510-12 C2(Nm2 electron charge =-1.610-19 C electron mass=

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Page 1 of 5 Reitze/Kumar PHY2054 Exam 1 February 16, 2011 ************************************************************ Useful Constants: k e = 8.99×10 9 Nm 2 /C 2 ε 0 = 8.85×10 -12 C 2 /(Nm 2 ) electron charge = -1.6×10 -19 C electron mass= 9.11×10 -31 kg V=Volt N=Newton J=Joule m=Meter C=Coulomb g=9.8 m/s 2 "milli-" = 10 -3 "micro-" = 10 -6 "nano-"=10 -9 "pico="=10 -12 ************************************************************ 1. If the electric field has a magnitude of 4 N/C at a distance of 1 meter from an isolated point charge, at what distance (in m) is the magnitude of the electric field equal to (0.5, 6, 10) N/C? E = kq/r 2 . The information given here leads to kq = 4. Thus solving for r when E = (0.5, 6, 10) we get r 2 = (8, 4/6. 0.4). (1) (2.83, 0.82, 0.63 2. An electron traveling north enters a region where the electric field is uniform and points north. The electron will then: Because the charge of the electron is negative, the force on it, F = qE is pointed backwards and the electorn will slow down. (1) slow down (2) speed up (3) veer east (4) veer west (5) continue with the same speed in the same direction 3. Two charged particles are arranged as shown in the figure with the +2 C charge on the left and the -4 C charge on the right. In which region could a third particle, with charge +1 C, be placed so that the net electrostatic force on it is zero? It can be region I only. The electric field due to the charge +2C is pointed away from the charge while the one due to -4C is pointed towards it. In region 2, the two electric fields are in the same direction and get added. In region 3 they cancel but the larger charge being closer, always dominates. Only in region 1 can they cancel to yield a zero electric field. (1) Region 1 only (2) Region 1 and 2 only (3) Region 3 only (4) Region 1 and 3 only (5) Region 2 only +2C -4C Region 1 Region 2 Region 3
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Page 2 of 5 4. A 1 gram particle with a charge of 1 milliC starts from rest in a uniform electric field with magnitude. If the particle moves (5, 30, 50) m in 2 seconds, what is the magnitude of the electric field (in N/C)? Motion under constant acceleration (electric field) is described by x = qEt
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This note was uploaded on 10/13/2011 for the course PHY 2054 taught by Professor Avery during the Spring '08 term at University of Florida.

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PHY 2054 Exam 1 - Reitze/Kumar PHY2054 Exam 1 Useful Constants ke= 8.99109 Nm2/C2 0= 8.8510-12 C2(Nm2 electron charge =-1.610-19 C electron mass=

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