2. The following diagram shows a circular loop of wire in a uniform magnetic field that points out of the page.

Transcription

1 1. Two elecromagneic waves ravel hrough emp space. Wave A as a wavelengh of 700 nm (red ligh), while Wave B has a wavelengh of 400 nm (blue ligh). Which saemen is rue? A) Wave A ravels faser because i has a longer wavelengh. B) Wave B ravels faser because i has a higher frequenc. C) The speed of he wo waves depends on heir ampliudes. D) Boh waves ravel a speed c. E) The speed of he wo waves depends on heir polarizaion. 2. The following diagram shows a circular loop of wire in a uniform magneic field ha poins ou of he page. You now perform four separae eperimens: Eperimen I: Wih he loop held saionar, he srengh of he magneic field is graduall increased. Eperimen II: Wih he magneic field held consan, he loop is moved o he righ. The loop remains in he plane of he page and never eis he magneic field. Eperimen III: Wih he magneic field held consan, he loop is shrunk o one half is iniial radius, alwas remaining wihin he plane of he page. Eperimen IV: Wih he magneic field held consan, he loop is roaed clockwise abou is cener, alwas remaining wihin he plane of he page. In which of hese eperimens will here be an induced curren in he loop? A) I and III B) I, II, and IV C) III onl D) I onl E) I and IV

2 3. When elecrici reaches our house from he power compan, i has an rms volage of 8,500 V and a frequenc of 60 Hz. To achieve he desired 120 V (rms) household volage, a sep-down ransformer is used, as shown a righ. If he ouer ransformer coil (he one conneced o he high-volage line) conains 25,800 urns of wire, how man urns should he inner ransformer coil (he one conneced o our house) conain? V rms = 8,500 V A) 550 B) 360 C) D) E) Two plane mirrors mee a righ angles a he origin. An objec is placed a he poin (3,2), as shown here: Which diagram bes indicaes he locaion of all he images formed b he mirrors? (Images are shown as open circles.) A) B) C) D) E)

3 5. A circui conaining a capacior, an inducor, a generaor, and wo idenical ligh bulbs is consruced as shown. The generaor produces a peak emf of 10 V. The frequenc of he generaor can be varied. ω C L Bulb A Bulb B Eamine he following saemens abou his circui: I. Bulb A shines more brighl han bulb B a large frequencies. II. As approaches zero, bulb A goes ou and bulb B coninues o shine. III. The wo bulbs have equal brighness when 1 LC. Which saemen(s) are rue? A) I and II B) II and III C) I, II, and III D) III onl E) I and III 6. Lenz's law saes ha he direcion of an induced emf is such ha i opposes he change in magneic flu. If insead he opposie were he case (i.e. he induced emf reinforced he change in flu), wha fundamenal law of phsics would be violaed? A) No law would be violaed; he direcion jus happens o be his wa. B) Newon's second law. C) Conservaion of elecric charge. D) Gauss's Law. E) Conservaion of energ.

4 Quesions 7 and 8 refer o he following figure, which depics a plane elecromagneic wave. z E B E B E B 7. Eamine he following saemens abou his wave: I. The wave is propagaing in he + direcion. II. This wave could be produced b a charge oscillaing back and forh along he -ais. III. The wave is linearl polarized. Which saemen(s) are rue? A) I and III B) III onl C) I, II, and III D) I onl E) II onl 8. If ou waned o deec his wave using an anenna, i would be bes o use A) A linear anenna oriened parallel o he -ais, or a loop anenna ling in he - plane. B) A linear anenna oriened parallel o he -ais, or a loop anenna ling in he -z plane. C) A linear anenna oriened parallel o he z-ais, or a loop anenna ling in he -z plane. D) A linear anenna oriened parallel o he z-ais, or a loop anenna ling in he -z plane. E) A linear anenna oriened parallel o he -ais, or a loop anenna ling in he -z plane.

5 9. The Voager 1 spacecraf, launched in 1977 o eplore he ouer planes, is presenl abou 10 billion kilomeers awa--beond he orbi of Pluo. However, is radio ransmier coninues o send useful daa o scieniss on Earh. The rms srengh of he elecric field 10 from hese ransmissions is abou V/m. If he signal is received b a radio dish wih an area of 900 m 2, wha is he rms power inciden on he dish? A) W B) W C) W D) W E) W 10. A real objec is placed 25 cm awa from a mirror wih a radius of curvaure of 30 cm, as shown here: Objec C The image formed b his mirror will be: A) real, uprigh, and magnified. B) virual, uprigh, and reduced. C) real, uprigh, and reduced. D) real, invered, and magnified. E) virual, invered, and magnified.

6 Quesions 11 and 12 refer o he following AC circui. I consiss of an inducor and a resisor in series wih a generaor of frequenc f. Inernal resisance of he generaor is negligible. f L R 11. The impedance of his circui is: A) R L B) R 2 L 2 C) R 2 2 fl 2 D) R 2 L 2 E) 2 R 2 f fl 12. In his circui: A) resonance will occur if he circui is driven a he appropriae frequenc. B) he generaor performs no work. C) all of he power is dissipaed in he resisor. D) he volage and he curren are in phase. E) he curren leads he volage, bu if he resisor and he inducor rade posiions hen he volage will lead he curren.

7 13. You are sanding 3.0 m awa from he shore of a calm pond ha is 26 m wide. An oak ree grows on he opposie shore. From where ou are sanding, wih our ees 1.6 m above he surface of he waer, ou can jus see he reflecion of he reeop in he waer neares o our fee. How all is he ree? A) 18.7 m B) 13.9 m C) 24.6 m D) 21.8 m E) 15.2 m 14. Vericall polarized ligh wih inensi S 0 passes hrough wo successive polarizers. The firs has is ransmission ais oriened a 30 from he verical. The second has is ransmission ais oriened a 60 from he verical. The inensi of he ligh ha emerges from he second polarizer is A) 9 16 S 0 B) 1 4 S 0 C) 3 8 S 0 D) 3 16 S 0 E) zero

8 15. In he circui shown here, a conducing bar is free o move on wo parallel meal rails. The wo rails are conneced b a resisor R. A uniform magneic field of srengh B, direced ou of he page, covers he enire region of his diagram. R B ou of page You now move he bar as shown in he posiion vs. ime graph a righ. Which of he graphs below bes depics he curren in he resisor as a funcion of ime? A posiive value means ha he curren is circulaing clockwise; a negaive value means ha he curren is circulaing counerclockwise. I A) B) I I C) I D) E) I

9 16. You are designing a generaor ha will produce a maimum emf of 170 V when roaed a an angular speed of 377 rad/s in a magneic field of srengh T. You plan o do his b winding wire around a square frame whose sides have lengh 12 cm. How man urns of wire should ou use? A) 891 B) 1370 C) 626 D) 1020 E) A shaving/makeup mirror produces an image ha is uprigh and magnified b a facor of 2.5 when our face is 32 cm from he mirror. Wha is he radius of curvaure of he mirror? A) 84 cm B) 128 cm C) 46 cm D) 224 cm E) 107 cm

10 18. A disan gala is receding from us a a speed of m/s. An alien in ha gala is beaming ou a disress signal whose wavelengh he measures o be 662 nanomeers (nm). Wha wavelengh do ou measure for his signal? A) 610 nm B) 680 nm C) 662 nm D) 730 nm E) 644 nm 19. In class, we performed he jumping ring demonsraion, in which a meal ring is placed on op of a verical solenoid. A =0, a swich was closed, causing he curren in he solenoid o rise ver quickl from zero o some large value. The ring jumped off he solenoid and hi he ceiling of he lecure hall. Call his he original version of his eperimen. Here are hree possible variaions: I. Same as he original version, bu he meal ring is replaced b a non-conducing rubber ring. II. Same as he original version, bu a noch is removed from he ring, so ha i resembles he leer C. III. Wih a large, sead curren running hrough he solenoid, a meal ring is placed on op of he solenoid. A =0, a swich is opened, causing he curren o fall rapidl o zero. In which variaion(s) will he ring jump up from he solenoid? A) III onl B) I onl C) II onl D) none of hese E) I, II, and III

11 20. The curren in a cerain circui is increased a a consan rae from 2.0 A o 7.0 A over a period of 2.0 s. During his ime, an induced emf of 72 mv is observed in he circui. Wha is he self-inducance of his circui? A) 48 mh B) 29 mh C) 68 mh D) 18 mh E) 33 mh Before ou go: END OF EXAM 1. Check our work carefull. Make sure ou have ransferred all our answers o our scanron. 2. BE SURE YOU HAVE FILLED IN YOUR NAME, SECTION, UM-ID, AND EXAM VERSION NUMBER ON YOUR SCANTRON. Failure o do hese hings correcl can resul in our grade being delaed or incorrec. 3. Turn in our eam and our scanron a he fron of he room. Eams will be reurned o ou in our discussion secion on Tuesda.