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phys fall 2008 key exam3

phys fall 2008 key exam3 - Physics 222 ABC EXAM#3(Chapters...

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Unformatted text preview: Physics 222 ABC EXAM #3 (Chapters 28-32) FALL 2008 Name: . Instructions: For the appropriate problems circle the letter corresponding to the correct answer. If you are sure that no correct answer is showmyou should write your answer in space (0 ~ ~ . Some questions require filling the blanks. ‘ Note ‘ that some problems/questions have more than one (I) correct answer. For those problems/questions you should give all the correct answers. The numbers in the [ 1 represent the points for the problem. [14.] 1. Matching: Write the number of the items on the right in the space in front of the correct answers on the left. ( 2,) The 2 component of the electron’s spin magnetic dipole moment 1. Q (C) electric charge (5") Bohr magneton 2. S. = m,h/2n, m, = (+/~)( 1/2) ( 7) In a mass-spring system, the spring constant k (N/m) 3. L (H), inductance corresponds to . (3 ) In a mass-spring system, M (kg) corresponds to 4. I...“ z = nth/21:, m; = 0, +/-l, +/-2, +/-m¢ ma) ( ‘ ) In a mass-spring system, v (in/s) corresponds to 5. p, = eh/41cm ‘ ( i ) In a mass-spring system, x (m) corresponds to 6. i (A) current ( I] ) The 2 component of the electron’s orbital angular momentum 7. l/C (F)", Capacitance [6] 2. A fully charged ideal capacitor is connected in parallel with an ideal inductor using wires that have some resistance. The circuit now begins to oscillate. Circle each of the true statements below? (Note that there is more than one true statement.) Answers: (a) For the circuit the inductive reactance will always cancel out the capacitive reactanoe to giVe resonance.» (b) This is an example of an undamped oscillator. It is possrble to keep the oscillations going indefinitely by'insezting an alternating emf source that has the right voltage amp do and frequency, in series with the capacitor and inductor. Energy will be lost during each cy of the oscillations and the oscillations will eventually step. (e) The oscillations will ntinue indefinitely (i.e, for ever). is is an example of a damped oscillator. For the RLC circuitat the right R = 56.7 mi), C = 0.82 an L = 475 pH, and £(t) = 13.8V sin [21:04.3 MHz)t]. Use this information to answer problems 3, 4, 5 and 6. [8] 3. Determine the re r: g e of the capacitor in the circuit ! R L Answer: (a). 5.40 mg. @3 13.6 mfl. (c). 22.5 m. (d). 49.0 :2. c 1 (e). 67.0 min. (f) at) [8] 4. The impedance in the circuit is AnSWer: (a) 13.7 m. (b) 33.7 mi). @617 mfl. (d) 73.7 mi). (e) 93.7 m. (f) [8] 5. Determine the phase ugle to complete the following statement: . , "" ":21; ’ ; t“... 51:31 is given hyie’ ) sis; mAsin l21r(i-i.3»MHz)t.- ¢]. . a ,. u - - . . e Allbhcr.”.1.. (n) 30.0‘ (c) 55.0“ (d) 57.6 “. (e) 8&4". (t) __ . [5] 6. Whi of the phasor diagrams below would best describe the current and voltage relationships of the circuit in problem 3? Answers: " (iii) VR 5 (iv) VR VL t (0d i 6 ’7 a. VG Vc VL that condition? Answer: (a) (i). [10) 8. The magnetic field through the three-qu circular loop changes according to the relation Rt) = (790 - 5.20?) uT, where t is in seconds. The resistance of the loop is 8.40 Inn. What is the magnitude and . direction (circle the correct choice) of the current that is induced in the loop at t = 3.0 seconds? (The radius r of the loop is 3.80 cm.) Answer: (a) 72AM. (b) 59.5 uA. (c) 32.4 m. (d) 28.4 11A. (e 12.6 MA. (f) __ . Direction: CW or w erpz‘ ..‘....,;.i.i _. _ > For Problems 14 & 15 use the information below: Physics 222 EXAM #3 SPRING 2007 A Name: . [8] 9. Four of the following equations are known as the Maxwell‘s equations. Circl each of those four equations. [Bods=,uo(i +id)m. (b) IE0 =- daft“) .‘ (c) Hzeq‘x—‘gtfl. ’IBodA=O. (e) id=lk£o(¢g)- @IEIdA= Eods=- Mi“). [1 l] 10. Match the equations given in problem 9 with the statements below by writing the letter of the equation in the space by the correct statement(s). - Statements: Q This is a fictitious current (i.e., as the current between the lates of a capacitor). 4 Suggests that electric chargescan be of two types having the same magnitude of charge. Gauss's Law for electrostati . ’ Farraday’s Law. A changing magnetic field produces an electric field an A changing electric field pro uces a magnetic field. Suggests that isolated electric charges can be found in nature. suggests that there is a connection between ' t and'electrtc and magnetic fields. __Q_\_. Ampere-Maxwell's Law. Gauss's Law for magnetism. Predicts that no isolated magnetic monopoles exist in nature. [6] 11. A 7.20 mg resistor and 5.80 uH'inductor are connected in series across an ideal battery that supplies 9.0 V. How much energy is stored in the magnetic field of the inductor when L the magnetic field beco es stable? + l . ) Answer: (a) 1.00 J. @453 J. (e) 9.60 J. (1) a (c) 5.50 J. (d) 7.62 J. [8] 12. Two identical shaped pieces of wire are placed as shown in the figure. 1, = if 4.5 A and i, and bare in opposite directions. If the magnitude of the magnetic field at P due to only i, is B, (T), the magnitude of the net magnetic field at P due / to i, and l, is Answer: (a)0(T). @ZB. (T). (c) 0.5B1 (T). (d) 4.581 (T). (e) B,/4.5 (T). ‘ (t) An induced current will be set up in the conducting loop. The direction of the magnetic field at P the center of the circle, due t this 'nduced curre t is Answer: (at) There is no magnetic field at P. (b) To the lefi. (c) To the right ' ‘ , (e) Perpendicularly o: t of the was. . a". _;...,gs.., Three concentric current carrying cylindrical conductors A, B and C, pass through the paper. The direction of each current is indicated by O or x. I}. = 14.0A, i3 = 17.0 A and lc= 24.0 A. [5] 14. The net current (magnitude and direction) through the cross section shown is Answer:l.0 A. (b) 34.0 A. (c) 19.0 A. (a) 10.0 A. (e) 3.00 A. (1) . Directifi W“ 1k; M [10] 15. Determine the magnetic field (magnitude and direction) at a di gee of 5.00 cm from the center of the cylinders. Answer: (a) 96.0 u’l‘. (b) 34.0 in“. (c) 72.0 1.1T. (a) 46.0 “T. 28.0 pr. (1) Direction: Ccn/ [12] 16. Six particles are moving when they suddenly enter a magnetic * " field B. The lines represent the paths of the particles in the magnetic field. . . . . . Match the path number with the charge or lack of charge on the particle. (Use + for positive, - for negative, or n for neutral ) 1 n , 2. -- 3. n 4. + , l 5. "' 6 ‘4' L} ...
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