ss_6 - 5. A resistive heating element is to be built from...

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Unformatted text preview: 5. A resistive heating element is to be built from tungsten wire 0.05 mm in diameter. The element should dissipate 50 Watts of power. The resitivity of tungsten is 9 uQ—cm. (a) Estimate the length of the wire required for such a device operating at 110 V. (b) Suppose the temperature dependence of the resistivity is included in the calculation. Would the design now call for a longer or shorter wire relative to when the T—dependence was ignored? ‘ (c) What, if any, effect would a nick in the wire have on its performance? onLb mung; W Lagxgmxm W4:— Nzouus m. MCch bosom $9. WWW WW: Wfighm two“) Hz. (was? m met}; “in Emu Mews W M m. L___# 8. What typical metals and what general electrical properties (high, intermediate, low resistivity; temperature coefficient of resistivity) would you recommend for the following applications: a. electrical furnace windings; b. electrical power transmission lines; fl T 0. electrical resistance standards. ES T D 3r l [V Cofififizctfij— fi‘lfiwx f0 N38 was wk To mea mid—ax RES‘SW W 9am WWW . © km {)0 - 54 ka‘" . lWDV-WEC scams M— TWW‘E awagk Samoa; M1 W - © Low m moo as $3: Mamm- fibo QfiSsxSTNiQ uncut.)th HEW W9 have: \V WLMLGEL UNMKLS. 13. Consider a capacitor with a plate area of 1 mm x 1 mm and a plate separation of 100 pm. If the gap is filled with a titanate Whose dielectric constant is 50, what is the maximum charge that can be stored at when for an applied voltage of 5 V. If the titanate is removed and replaced by air, what plate area will be required to store this same amount of charge? / .1 w ""ffif:21117*"‘\nh M, \w m "*f::::::;.:;:i_ \l \- \ 6/ \Mi‘x 0: CV == Léa E— \J L A .z P 1 {€05 Ems no“ %\ \ks \J\ : 7.2 unfit Gg ka Wm‘ [- 15. Suppose an insulating piece of pure SiO; (silicon dioxide) glass has a bandgap, Eg, of 6eV. (a) Quantitativer Show that this glass would be transparent to violet light with a wavelength of 30011111. (in) Suppose the SiOz contains a small concentration of impurities which introduce a donor level in the gap 1.0 eV below the bottom of the conduction band. Will the glass still be transparent to the violet light? Justify your answer. V * 9n a fin: bow» is 10‘0"“ Mum-m “ V “*— an (New twice: We 6 GM (3; gem-CREW wwcu :%.626x\5m§4¢3 moth M SWOM ’ Q031— Ms To ‘6“:th was.» sagmom boy“) “mass "ms: gamma ' @AUJS “MB "Wm wt = WARN Sox \Qo3 sous 3% m h 1::- e vwmwv» .' . “MR asses wok pvt train-t: he we: mstm V0 3" W M xii» 7:09 NM LAW-T. "v: (is. M) N WZW‘E‘S a} W 59%3. 16. How many atoms are contained in 1 cubic centimeter of silicon? If silicon is doped with 1018 atomsfcm3 of boron, how much boron has been added in terms of atomic percent? 95“ '— 7.7:”) 43/0} twig : "2%.01 a/Wye; ‘ “Mix *’ goal no?) kiwi; \Qs‘. : & mBXkY‘y‘ &/ch5\ L \{3-3 3 Wm; B éwwhurk Wow-5n as GM h" wT. 23. The band gap for pure silicon is 1.12 eV. The donor level for Sb doped into silicon is 0.039 eV below the bottom of the conduction band. At room temperature (300 K), compare the number of electrons excited into the conduction band for pure silicon and silicon doped with 10” Sb atomsfcmg’. Which of these materials has the higher electrical conductivity? Why? Cb ‘34 (‘x := D 9, ’KJ “76%;: 0.03% We Qb-kw “DEM-wadsk-Dma u.)ka “Aw; ix Wm QWLOWCM Coastal»;th mm.) M watt ‘3. .\ __, ._ 09km Wt" Wow "WWW'cML/ld'z‘ W51 364;: My a9) as mme watt 8 MD \ - Q Li I sic/Rum \m ‘Pqu \- 5(a) w we we». WK 25. Contrast the effect on the electrical conductivity of doping pure Si with 1 wt% Alto that of alloying pure A1 with 1 wt% Si. What is the approximate increase or decrease in electrical conductivity in each case? cow 8: \3 mm “W N M motif ‘8 {x MRNLK \L kktoy . We WU \‘W ’18 Wm M M. FKKDYIJJ £fiW Wt. W\U\Y75 vcwsagplsw V67 k Pat/W- e, \05 KMQ3FC a? m \kMRfifi); \ino%h§:ufi‘7 afir e,“ same/AWE. mom gmxm W8 351 $\QC\}>E WECW\WWS_ WW k\ \8 M \‘D 8‘ “Va WSULT CWCRk f» sx VHW: gwtmgum. m ELLE; {fly (gay-gram &~ maman \mcamms 26. List the dominant (majority) charge carrier(s) in each of the foilowing semiconductors: a. intrinsic Si 13. intrinsic Ge c. Si doped with P (at iow temperature) d. Ge doped with P (at low temperature) e. GaAs doped with Zn (at low temperatures) ® We mk- tmoet Cepcfimw‘) <3; waif» we metre-ass, cmmgfit 95- 5A k3- ...
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ss_6 - 5. A resistive heating element is to be built from...

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