Quston 1 Qustons If th only nstrumnt you had n your posssson to dtct C voltag sgnals was an audo spakr, how could you us t to dtrmn whch of two C voltag wavforms has th gratst prod? Hz FUNCTION GENERTOR 1 10 100 1k 10k 100k 1M Spakr coars fn DC output Hz FUNCTION GENERTOR 1 10 100 1k 10k 100k 1M coars fn DC output fl 00387 Quston 2 What s th dffrnc btwn DC and C lctrcty? Idntfy som common sourcs of ach typ of lctrcty. fl 00028 Quston 3 ll othr factors bng qual, whch posssss a gratr potntal for nducng harmful lctrc shock, DC lctrcty or C lctrcty at a frquncy of 60 Hrtz? B sur to back up your answr wth rsarch data! fl 03289 Quston 4 Suppos a DC powr sourc wth a voltag of 50 volts s connctd to a 10 Ω load. How much powr wll ths load dsspat? Now suppos th sam 10 Ω load s connctd to a snusodal C powr sourc wth a pak voltag of 50 volts. Wll th load dsspat th sam amount of powr, mor powr, or lss powr? Explan your answr. fl 00401 1
Quston 5 Is t approprat to assgn a phasor angl to a sngl C voltag, all by tslf n a crcut? 24 VC 100 Ω What f thr s mor than on C voltag sourc n a crcut? 24 VC 100 Ω 15 VC fl 00496 Quston 6 If th powr wavform s plottd for a rsstv C crcut, t wll look lk ths: p Tm What s th sgnfcanc of th powr valu always bng postv (abov th zro ln) and nvr ngatv (blow th zro ln)? fl 02174 2
Quston 7 If a snusodal voltag s appld to an mpdanc wth a phas angl of 90 o, th rsultng voltag and currnt wavforms wll look lk ths: Tm Gvn that powr s th product of voltag and currnt (p = ), plot th wavform for powr n ths crcut. lso, xplan how th mnmonc phras ELI th ICE man appls to ths wavforms. fl 00632 Quston 8 If a snusodal voltag s appld to an mpdanc wth a phas angl of -90 o, th rsultng voltag and currnt wavforms wll look lk ths: Tm Gvn that powr s th product of voltag and currnt (p = ), plot th wavform for powr n ths crcut. lso, xplan how th mnmonc phras ELI th ICE man appls to ths wavforms. fl 00633 3
Quston 9 Suppos that a varabl-voltag C sourc s adjustd untl t dsspats th xact sam amount of powr n a standard load rsstanc as a DC voltag sourc wth an output of 120 volts: Standard load rsstancs (qual numbr of ohms) 120 V In ths condton of qual powr dsspaton, how much voltag s th C powr supply outputtng? B as spcfc as you can n your answr. fl 00402 Quston 10 Dtrmn th RMS ampltud of ths snusodal wavform, as dsplayd by an osclloscop wth a vrtcal snstvty of 0.2 volts pr dvson: fl 01818 4
Quston 11 Solv for all voltags and currnts n ths srs RC crcut, and also calculat th phas angl of th total mpdanc: 220n 3k3 fl 01849 48 V pak 30 Hz 5
Quston 12 studnt masurs voltag drops n an C crcut usng thr voltmtrs and arrvs at th followng masurmnts: V V V OFF V OFF COM COM V V OFF COM Upon vwng ths masurmnts, th studnt bcoms vry prplxd. rn t voltag drops supposd to add n srs, just as n DC crcuts? Why, thn, s th total voltag n ths crcut only 10.8 volts and not 15.74 volts? How s t possbl for th total voltag n an C crcut to b substantally lss than th smpl sum of th componnts voltag drops? nothr studnt, tryng to b hlpful, suggsts that th answr to ths quston mght hav somthng to do wth RMS vrsus pak masurmnts. thrd studnt dsagrs, proposng nstad that at last on of th mtrs s badly out of calbraton and thus not radng corrctly. Whn you ar askd for your thoughts on ths problm, you ralz that nthr of th answrs proposd thus far ar corrct. Explan th ral rason for th dscrpancy n voltag masurmnts, and also xplan how you could xprmntally dsprov th othr answrs (RMS vs. pak, and bad calbraton). fl 01566 6
Quston 13 paralll RC crcut has 10 S of suscptanc (B ). How much conductanc (G ) s ncssary to gv th crcut a (total) phas angl of 22 dgrs? 22 o G =??? B = 10 µs G =??? B = 10 µs fl 02090 Quston 14 paralll C crcut draws 8 amps of currnt through a purly rsstv branch and 14 amps of currnt through a purly nductv branch: I R = 8 θ I total =??? I L = 14 8 14 Calculat th total currnt and th angl Θ of th total currnt, xplanng your trgonomtrc mthod(s) of soluton. fl 02089 Quston 15 paralll C crcut draws 100 m of currnt through a purly rsstv branch and 85 m of currnt through a purly capactv branch: I total =??? θ I R = 100 m I C = 85 m I R = 100 m I C = 85 m Calculat th total currnt and th angl Θ of th total currnt, xplanng your trgonomtrc mthod(s) of soluton. fl 02091 7
Quston 16 tchncan s troublshootng a powr supply crcut wth no DC output voltag. Th output voltag s supposd to b 15 volts DC: Fus TP3 TP2 TP4 TP1 TP5 TP8 TP6 TP7 - - TP10 DC voltag output TP9 Th tchncan bgns makng voltag masurmnts btwn som of th tst ponts (TP) on th crcut board. What follows s a squntal rcord of hs masurmnts: 1. V TP 9 TP 10 = 0 volts DC 2. V TP 8 TP 7 = 0 volts DC 3. V TP 8 TP 5 = 0 volts DC 4. V TP 6 TP 7 = 0 volts DC 5. V TP 4 TP 5 = 0 volts C 6. V TP 1 TP 3 = 0 volts C 7. V TP 1 TP 2 = 116 volts C Basd on ths masurmnts, what do you suspct has fald n ths supply crcut? Explan your answr. lso, crtqu ths tchncan s troublshootng tchnqu and mak your own suggstons for a mor ffcnt pattrn of stps. fl 00795 8
Quston 17 tchncan s troublshootng a powr supply crcut wth no DC output voltag. Th output voltag s supposd to b 15 volts DC: Fus TP3 TP2 TP4 TP1 TP5 TP8 TP6 TP7 - - TP10 DC voltag output TP9 Th tchncan bgns makng voltag masurmnts btwn som of th tst ponts (TP) on th crcut board. What follows s a squntal rcord of hr masurmnts: 1. V TP 1 TP 2 = 118 volts C 2. V TP 3 TP 2 = 0 volts C 3. V TP 1 TP 3 = 118 volts C 4. V TP 4 TP 5 = 0.5 volts C 5. V TP 7 TP 8 = 1.1 volts DC 6. V TP 9 TP 10 = 1.1 volts DC Basd on ths masurmnts, what do you suspct has fald n ths supply crcut? Explan your answr. lso, crtqu ths tchncan s troublshootng tchnqu and mak your own suggstons for a mor ffcnt pattrn of stps. fl 00796 9
Quston 18 tchncan s troublshootng a powr supply crcut wth no DC output voltag. Th output voltag s supposd to b 15 volts DC: Fus TP3 TP2 TP4 TP1 TP5 TP8 TP6 TP7 - - TP10 DC voltag output TP9 Th tchncan bgns makng voltag masurmnts btwn som of th tst ponts (TP) on th crcut board. What follows s a squntal rcord of hs masurmnts: 1. V TP 9 TP 10 = 0 volts DC 2. V TP 1 TP 2 = 117 volts C 3. V TP 1 TP 3 = 117 volts C 4. V TP 5 TP 6 = 0 volts C 5. V TP 7 TP 8 = 0.1 volts DC 6. V TP 5 TP 4 = 12 volts C 7. V TP 7 TP 6 = 0 volts DC Basd on ths masurmnts, what do you suspct has fald n ths supply crcut? Explan your answr. lso, crtqu ths tchncan s troublshootng tchnqu and mak your own suggstons for a mor ffcnt pattrn of stps. fl 00797 10
Quston 19 tchncan s troublshootng a powr supply crcut wth no DC output voltag. Th output voltag s supposd to b 15 volts DC, but nstad t s actually outputtng nothng at all (zro volts): Fus TP2 TP3 T1 TP4 TP1 TP5 TP8 D3 D1 TP6 D2 D4 TP7 TP9 - - C1 TP10 DC voltag output Th tchncan masurs 120 volts C btwn tst ponts TP1 and TP3. Basd on ths voltag masurmnt and th knowldg that thr s zro DC output voltag, dntfy two possbl faults that could account for th problm and all masurd valus n ths crcut, and also dntfy two crcut lmnts that could not possbly b to blam (.. two thngs that you know must b functonng proprly, no mattr what ls may b faultd). Th crcut lmnts you dntfy as thr possbly faultd or proprly functonng can b wrs, tracs, and connctons as wll as componnts. B as spcfc as you can n your answrs, dntfyng both th crcut lmnt and th typ of fault. Crcut lmnts that ar possbly faultd 1. 2. Crcut lmnts that must b functonng proprly 1. 2. fl 02306 11
Quston 20 Suppos ths powr supply crcut was workng fn for svral yars, thn on day fald to output any DC voltag at all: Fus T 1 D 1 D 2 115 VC RMS D 3 D 4 C 1 Whn you opn th cas of ths powr supply, you mmdatly notc th strong odor of burnt componnts. From ths nformaton, dtrmn som lkly componnt faults and xplan your rasonng. fl 03708 12
nswr 1 nswrs Connctng th spakr to ach C voltag sourc, on at a tm, wll rsult n two dffrnt audo tons output by th spakr. Whchvr ton s lowr n ptch s th wavform wth th gratst prod. nswr 2 DC s an acronym manng Drct Currnt: that s, lctrcal currnt that movs n on drcton only. C s an acronym manng ltrnatng Currnt: that s, lctrcal currnt that prodcally rvrss drcton ( altrnats ). Elctrochmcal battrs gnrat DC, as do solar clls. Mcrophons gnrat C whn snsng sound wavs (vbratons of ar molculs). Thr ar many, many othr sourcs of DC and C lctrcty than what I hav mntond hr! nswr 3 From a prspctv of nducng lctrc shock, C has bn xprmntally provn to possss gratr hazard than DC (all othr factors bng qual). S th rsarch of Charls Dalzl for supportng data. nswr 4 50 volts DC appld to a 10 Ω load wll dsspat 250 watts of powr. 50 volts (pak, snusodal) C wll dlvr lss than 250 watts to th sam load. nswr 5 Phasor angls ar rlatv, not absolut. Thy hav manng only whr thr s anothr phasor to compar aganst. ngls may b assocatd wth multpl C voltag sourcs n th sam crcut, but only f thos voltags ar all at th sam frquncy. nswr 6 Postv powr rprsnts nrgy flowng from th sourc to th (rsstv) load, n ths cas manng that nrgy nvr rturns from th load back to th sourc. nswr 7 p Tm Th mnmonc phras, ELI th ICE man ndcats that ths phas shft s du to an nductanc rathr than a capactanc. 13
nswr 8 p Tm Th mnmonc phras, ELI th ICE man ndcats that ths phas shft s du to a capactanc rathr than an nductanc. nswr 9 120 volts C RMS, by dfnton. nswr 10 Th RMS ampltud of ths wavform s approxmatly 0.32 volts. nswr 11 V C = 47:56 volts pak V R = 6:508 volts pak I = 1:972 mllamps pak Θ Z = 82:21 o Follow-up quston: what would w hav to do to gt ths answrs n unts RMS nstad of unts pak? nswr 12 C voltags stll add n srs, but phas must also b accountd for whn dong so. Unfortunatly, multmtrs provd no ndcaton of phas whatsovr, and thus do not provd us wth all th nformaton w nd. (Not: just by lookng at ths crcut s componnts, though, you should stll b abl to calculat th corrct rsult for total voltag and valdat th masurmnts.) I ll lt you dtrmn how to dsprov th two ncorrct xplanatons offrd by th othr studnts! Challng quston: calculat a st of possbl valus for th capactor and rsstor that would gnrat ths sam voltag drops n a ral crcut. Hnt: you must also dcd on a valu of frquncy for th powr sourc. nswr 13 G = 24.75 S Follow-up quston: how much rsstanc s ths, n ohms? 14
nswr 14 I total = 16.12 amps Θ = 60.26 o (ngatv, f you wsh to rprsnt th angl accordng to th standard coordnat systm for phasors). Follow-up quston: n calculatng Θ, t s rcommndd to us th arctangnt functon nstad of thr th arcsn or arc-cosn functons. Th rason for dong ths s accuracy: lss possblty of compoundd rror, du to thr roundng and/or calculator-rlatd (kystrok) rrors. Explan why th us of th arctangnt functon to calculat Θ ncurs lss chanc of rror than thr of th othr two arcfunctons. nswr 15 I total = 131.2 m Θ = 40.36 o Follow-up quston: n calculatng Θ, t s rcommndd to us th arctangnt functon nstad of thr th arcsn or arc-cosn functons. Th rason for dong ths s accuracy: lss possblty of compoundd rror, du to thr roundng and/or calculator-rlatd (kystrok) rrors. Explan why th us of th arctangnt functon to calculat Θ ncurs lss chanc of rror than thr of th othr two arcfunctons. nswr 16 Th fus s blown opn. Follow-up quston: wth rgard to th troublshootng tchnqu, ths tchncan sms to hav startd from on nd of th crcut and movd ncrmntally toward th othr, chckng voltag at almost vry pont n btwn. Can you thnk of a mor ffcnt stratgy than to start at on nd and work slowly toward th othr? nswr 17 Th transformr has an opn wndng. Follow-up quston #1: wth rgard to th troublshootng tchnqu, ths tchncan sms to hav startd from on nd of th crcut and movd ncrmntally toward th othr, chckng voltag at almost vry pont n btwn. Can you thnk of a mor ffcnt stratgy than to start at on nd and work slowly toward th othr? Challng quston: basd on th voltag masurmnts takn, whch do you thnk s th mor lkly falur, an opn prmary wndng or an opn scondary wndng? Follow-up quston #2: how could you tst th two wndngs of th transformr for a possbl opn fault? In othr words, s thr anothr typ of masurmnt that could vrfy our hypothss of a fald wndng? nswr 18 Thr s an opn fault btwn TP4 and TP6. Follow-up quston: wth rgard to th troublshootng tchnqu, ths tchncan sms to hav startd from on nd of th crcut and movd ncrmntally toward th othr, chckng voltag at almost vry pont n btwn. Can you thnk of a mor ffcnt stratgy than to start at on nd and work slowly toward th othr? nswr 19 I ll lt you and your classmats fgur out som possblts hr! 15
nswr 20 Shortd capactor, opn transformr wndng (as a rsult of ovrloadng), shortd dod(s) rsultng n blown fus. 16