Phy207В В В В ExamВ IIВ (Form1)В В В В В В В В В В ProfessorВ ZuoВ В В В В В В В В В В FallВ SemesterВ 2014  “OnВ myВ honor,В IВ haveВ neitherВ receivedВ norВ givenВ aidВ onВ thisВ examination” Signature:______________________В В В Name:___________________В #1‐13В В #14В В TotalВ В IDВ number:___________________В В EnterВ yourВ nameВ andВ FormВ 1В (FM1)В inВ theВ scantronВ sheet.В В AttemptВ allВ problems.В MultipleВ choiceВ questionsВ areВ worthВ 5ptsВ eachВ andВ theВ essayВ problemВ isВ 40В ptsВ (5В extraВ ptsВ ifВ youВ doВ all).В ThereВ isВ aВ formulaВ sheetВ attachedВ theВ end.В В ThisВ isВ aВ closedВ bookВ exam,В youВ mustВ workВ independently!В NoВ collaborationВ isВ allowed.В В ProhibitedВ items:В anyВ electronicВ devicesВ includingВ cellВ phonesВ andВ calculators,В pens,В backpacks,В notes,В books.В В AnyoneВ foundВ cheatingВ duringВ theВ examВ willВ automaticallyВ receiveВ an “F” gradeВ forВ theВ courseВ andВ sentВ toВ theВ honor’sВ court.В В В Put an X next to your discussion section: [ ] Dr. Mezincescu 5P, 11:00 – 11:50 a.m. [ ] Dr. Curtright 5Q, 12:30 – 1:20 p.m. [ ] Dr. Zuo 5R, 2:00 – 2:50 p.m. [ ] Dr. Zuo 5S, 3:30 – 4:20 p.m. [ ] Dr. Liu 5T, 5:00 – 5:50 p.m. (For the next two problems) A parallel plate capacitor is made of two square sheets of metals of side length L with a separation d between each other. Half of the space is filled and the other half empty. The filled half is filled with two dielectrics with dielectric constant k1 and k2, as shown. 1) Find the capacitance of the capacitor A) B) 1 C) D) E) 2) Find the charge on the area just above the filled space if k1=2, k2=4. A) Q , B) Q, C) Q, D) Q, E) none of above 3) In the circuit shown in the figure, the capacitors are initially uncharged. The switch is first thrown to position A and kept there for a long time. It is then thrown to position B. Let the charges on the capacitors be Q1, Q2, and Q3 and the potential differences across them be V1, V2, and V3. Which of the following conditions must be true with the switch in position B? A) V1 = V2 = V3 B) V1 + V2 = V3 C) V3 = V0 D) Q1 = Q2 = Q3 E) Q1 + Q2 = Q3 4) When a potential difference of 10 V is placed across a certain solid cylindrical resistor, the current through it is 2 A. If the solid is compressed such that the diameter of this resistor is now twice as much as the original and the total volume remains the same, the current will be A) 8 A, B) 1/4 A, C) 1/8 A , D) 16 A, E) 32 A. В For the next three problems, consider a multiloop circuit shown in the figure. It is not necessary to solve the entire circuit. 5) Compared to the polarity shown in the figure, the emf Оµ1 is closest to A) -5 V, B) 5 V, C) 45 V, D) 51 V, E) -51 V. 6) What is current I1? A) 5A, B) 2A, C) A, D) A, E) none of above 7) What is current I2? A) 5A, B) 7A, C) 3A, D) 0A, E) -3A (For the next three problems) Consider the circuit shown below, the capacitors are all initially uncharged, the connecting leads have no resistance, the battery has no appreciable internal resistance, and the switch S is originally open. 8) Just after closing the switch S, what is the current in the 15.0-О© resistor? A) 0.00 A, B) 1.67 A, C) 2.50 A, D) 3.33 A, E) 5.00 A 9) What is the current going through the battery right after closing the switch? A) 0 A, B) A, C) A, D) A, E) A 10) After the switch S has been closed for a very long time, what is the potential difference across the 28.0-ОјF capacitor? A) 0.00 V, B) 25.0 V, C) 3.33 V, D) 37.5 V, E) 50.0 V В В 11) Ions having equal charges but masses of M and 2M are accelerated through the same potential difference and then enter a uniform magnetic field perpendicular to their path. If the heavier ions follow a circular arc of radius R, what is the radius of the arc followed by the lighter? A) 4R, B) 3R, C) 2 R, D) R/ 2 , 12) An electron moving with a velocity = 5.0 Г— 107 m/s Г® enters a region of space where perpendicular electric and a magnetic fields are present. The electric field is through the region without being deflected? A) = +2.0 Г— 10-4 T Дµ B) = -2.0 Г— 10-4 T Дµ C) = +2.0 Г— 10-4 T D) = -2.0 Г— 10-4 T E) = +5.0 Г— 10-4 T E) R/2 =10 kV/m Дµ. What magnetic field will allow the electron to go 13) A conducting bar of length 1.0 meter is being moved at a constant velocity of 1.0m/s from left to right on a track by an external force F as shown. A uniform magnetic field B=2.0T is directed out of the plane. The bar makes a good electrical contact and slides without friction. A constant force F=1.0N is applied. What is the current going through the resistor? A) ВЅ A B) 1 A C) 2 A D) 0 A E) I need to know the resistor R В В В В В В В 15) (40pt ) Two concentric spherical conducting shells with inner radius a and outer radius b for the inner shell and inner radius c and outer radius d for the outer shell are charged with q and –q, respectively. a) Find the electric field everywhere. b) Find the potential difference between the two conductors. c) Find the electric energy contained within a thin shell of radius r (b<r<c) and thickness dr. b) Find the total electric field energy. e) Find the capacitance of the capacitor. В bВ В aВ cВ В dВ В В Solution:В a)В EВ isВ zeroВ everywhereВ exceptВ forВ b<r<c,В whereВ E=kq/r2.В HereВ youВ canВ deriveВ itВ usingВ Gauss’sВ lawВ В 4 в€… b)В TheВ potentialВ differenceВ is ∆V=Vb‐Vc= В ).В c)В TheВ energyВ containedВ withinВ aВ thinВ shellВ canВ beВ calculatedВ usingВ ).В d)В TheВ totalВ energyВ isВ e)В ThereВ areВ twoВ waysВ toВ findВ theВ capacitance:В oneВ isВ usingВ C=Q/V=q/(kq(1/b‐1/c))=4 TheВ otherВ wayВ isВ toВ useВ U=(1/2)q2/C,В C=(1/2)q2/U=4 В В В 4 В В bc/(c‐b).В В bc/(c‐b).В В
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