Physics Quiz 3 in Course Physics 2212 Fall 2007, Quizzes of Physics

Download Physics Quiz 3 in Course Physics 2212 Fall 2007 and more Quizzes Physics in PDF only on Docsity! Choose a seat labeled A Physics 2212 G-K Test Form 301 Name Fall 2007 Quiz 3 Instructions: 1. Print your name, test form number (above), and nine-digit student number in the section of the answer card labeled “STUDENT IDENTIFICATION.” 2. Bubble your test form number in columns 1–3, skip column 4, then bubble in your student number in columns 5–13. 3. For each multiple-choice question, select the answer most nearly correct, circle this answer on your test, and bubble it in on your answer card. Do not put extra marks on the card. 4. Turn in your test and answer card and leave. Your score will be posted under “Course Standing” when it has been graded. Quiz grades become final when the next quiz is given. 5. You may use a calculator that cannot store letters, but no other aids. k = 1/(4πǫ0) = 8.99 × 10 9 N ·m2/C2 ǫ0 = 8.85 × 10 −12 C2/N ·m2 e = 1.60 × 10−19 C Blank space - Feel free to use this space for scratch work. If you have any hand-graded work here, please label it clearly, and make a note of this fact on the relevant page. Expansions for |x| ≪ 1: (1 + x)n ≈ 1 + nx ln(1 + x) ≈ x Standard Integrals: ∫ undu = un+1 n + 1 + C (n , −1) ∫ du u = ln |u| +C ∫ 1 1 + u2 du = tan−1(u) + C ∫ sin(u)du = − cos(u) +C ∫ cos(u)du = sin(u) +C ∫ u sin(u)du = sin(u) − u cos(u) + C ∫ u cos(u)du = cos(u) + u sin(u) + C ∫ eudu = eu +C ∫ ueudu = (u − 1)eu + C MULTIPLE-CHOICE: Circle your answers here and mark them on your answer card. 301 1. Capacitor circuit. A 16-µF capacitor is connected across an emf E = 4 V. If the value of the emf8 pts is changed to E = 8 V, what will be the value of the capacitance? (a) 16 µF (b) 8 µF (c) 4 µF (d) 2 µF (e) 32 µF 2. Potential energy. The initial configuration of 3 charges is an equilateral triangle of side d, as shown.8 pts All charges have the same magnitude Q0. Determine the change in potential energy of the system when the positive charge at top is moved to position P, midway between the other two charges. (a) ∆U = 0 (b) ∆U = 1 πǫ0 Q20 d (c) ∆U = 1 4πǫ0 Q20 d (d) ∆U = 1 2πǫ0 Q20 d (e) ∆U = − 1 2πǫ0 Q20 d Q0 −Q0 0Q P + + dd d/2d/2 FREE-RESPONSE: Show your work. Do not mark your answer card. 301 II. Equipotentials. The spherical conductor on the left in the figure is held at a potential of 100 V, and conducting plate on the right is held at -100 V. The small grid squares shown represent 1 cm on a side. Point A lies at a potential of 50 V, point B is at 0 V, and point C lies at -80 V (a) Within the gridded area, sketch the equipotential contours that pass through points A and C.5 pts C B A 100 V −100 V (b) Sketch the electric field lines passing through points A, B, and C.5 pts (c) Rank from largest to smallest, the electric field magnitudes |EA|, |EB|, and |EC | at points A–C.5 pts ∣ ∣ ∣ ∣ ∣ ∣ E ∣ ∣ ∣ ∣ ∣ ∣ > ∣ ∣ ∣ ∣ ∣ ∣ E ∣ ∣ ∣ ∣ ∣ ∣ > ∣ ∣ ∣ ∣ ∣ ∣ E ∣ ∣ ∣ ∣ ∣ ∣ (d) An electron (charge e = 1.6× 10−19 C, mass me = 9.11× 10−31 kg) is observed passing point A with5 pts a kinetic energy KA = 8.0 × 10−18 J. When it is subsequently observed at point B, what is its kinetic energy KB? KB = FREE-RESPONSE: Show your work. Do not mark your answer card. 301 III. Capacitor breakdown. In the circuit shown, C1–C3 are parallel-plate capacitors with identical plate areas A. Capacitor C1 has plate spacing d. In terms of C1, the other capacitors have the following values: C2 = 2C1; C3 = 3C1 Capacitor C2 can sustain a maximum internal field Em (for larger electric fields, the capacitor will be destroyed by “dielectric breakdown”). In what follows, express your final answers in terms of A, d, Em, and standard constants. (a) What is the maximum potential difference ∆Vm that can be sustained across capacitor C2? 5 pts ε 1C 2 C C3 + − ∆Vm = (b) What is the energy stored in capacitor C2 when its electric field is equal to Em?5 pts Um = (c) Determine the applied emf E for which the energy stored in C2 reaches its maximum value Um.10 pts E =