UnitExam2Asolutions

# UnitExam2Asolutions - ID A UCSD Physics 2B Answer Section...

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ID: A 1 UCSD Physics 2B Unit Exam 2A Potential & Capacitors Answer Section MULTIPLE CHOICE 1. ANS: B E =− V x , V y , V z Ê Ë Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ 33 V m ,0, 22 V m 2 y Ê Ë Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ V m i 8 + V m 2 y k 8 TOP: E from V 2. ANS: C By superposition, V = V 1 + V 2 = kq 1 r 1 + 2 r 2 = 2 a 2 + a 2 Ê Ë Á Á Á Á Á Á Á Á Á ˆ ¯ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ = 2 a = 2 9.0 × 10 9 N m 2 / C 2 Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 1.3 × 6 C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 6.1 × 2 m Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = 2.713 × 5 J / C The work required is W = QV = 2.9 × 6 C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 3.713 × 5 J / C Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ = 0.787 J = 787m J 3. ANS: D W = 1 2 CV 2 = 1 2 55 × 3 F Ê Ë Á Á Á ˆ ¯ ˜ ˜ ˜ 790 V () 2 = 1.72 × 4 J TOP: CAP Energy 4. ANS: B We solve this by equating the Energy gain through Work done on the electron by the field W = q Δ V with the final kinetic energy of the moving electron KE = 1 2 mv 2 W = KE v = 2 q Δ V m = 21 .6 0 × 19 C Ê Ë

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UnitExam2Asolutions - ID A UCSD Physics 2B Answer Section...

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