GIẢI CHI TIẾT THI LÝ L4-2011(ĐDT HN)

,f ' \ {^/' t l;" t* -uLh,- I Vo,{. Hnfng din gifri Od ttri thfr 6n 4 - ngiy 2712/2011 Mdn: Vit li - Mi d6 401 CAu l. Mhu do cria rubi do ion cr6m ph6t ra khi chuyOn t* trang th6i kfch thich vd tryng thr{i co bin -> Chqn A Ciu 2. tin sO g6c ro :2nlT :2n10,4: 5n(radls),-+ DO bii5n d4ng cria ld xo khi v{t cdn beng Al : glio2 = l0(5n)2 = 4cm. Khi ttua v4t dtin vi tri ld xo kh6ng bi6n d4ng rdi bu6ng nhg thi biOn ttQ dao cl6ng c0a Pg,e- vqt4=Al=4cm+chi6udei l6nnh6tctraldxoldl.u*:10+Al+A=40+4+4:48cm-+ChqnB. CAu 4. Theo bii to uys vi une lQch pha nhau 600+ ues tr6 pha 300 so vdi i; u4p lgch pha 750 so vdi uAs -+ ueN l€ch pha 450 so v6i i -+ ta c6 gidn tl6 vecto nhu hinh v6. Tir gidn dd vecto -+ Un: UnNcos45o = 60 Ji lZ:30JrV > u.ce = unlcos3Oo = loJi l(Ji tzl = 20 J6 v-+ chgn B. Ur.,ts CAU 5. Trong m4ch dao tlQng di6n tir : Di$n tich cria tg diQn vi cudrng tlQ ddng diQn trong m4ch lQch pha nhau 900-r A sai. Cuong tlQ ddng dipn trong m4ch vi ndng lugng tir trudng trong cuQn cAm cfrng nhu diQn tich cira tp itiQn vi nlng lugng <tiQn truong cria tp diQn khdng bi6n thi€n cirng tin s6 n€n kh6ng th6 so sdnh pha vdi nhau-+ B vd C sai. Cuong dQ ddng di€n trong mgch vd cdm rng tir cria t& trulng trong mpch bi6n thi6n cing pha+ D dring + Chgn D. CAu 6. Khi min cfch m{t phing hai khe le D thi khoing vdn li i = },Dla = 916 = l,5mm (l). Khi mnn dlch di 0,6m thi khoing vdn li i' = 914,5: 2mm -+ i'> i -+ D'> D-) D': D + 0,6 -) i' = l,(D + A,6)la (2) -+ Tir (l) vn (2) -) (D + 0,6)/D =211,5 -> D: 1,8m. Tir c6ng thric i= ]"Dla-) )r.: ialD = 1,5.10r. 0,48.10-3/1,8 = 0,4(pm) -+ Chqn B. Cdu 7. H4t a c6 kh6i lugng lon hsn r6t nhiAu so vdi hpt p ndn bi lech it hon so vdi hat B khi ditrong dign trudng -+ D sai + Chgn D. Cdu 8. t Mric culng ttQ dm d B nho hon d A 20dB -+ cudmg <tQ Am d B nho hcm d A le 102 lin -+ Ia/ls : (SB/SA)2 =100-+SB/SA=10;lellc:(SC/SA)2=[(SA+SB)/2SA]2=(l+SB/SAF/4:ll214=30,25+ChonB. Cdu 9. Lpc ma s6t sinh rac6c h4t mang tliQn n6n c6 tuong t6c tlign tt + Chgn D. Cdu 10. Chgn gdc th6 ning o v! tri cin bing, khi vflt d dQ cao h = FV3 thi th6 ndng cira vft bing ll3 cs ndng -+ EQng ning cria vft bing 213 co n6ng -+ mv2l2 = 2(mv,u*2lZ1l3 -+ vz = 2v* ]B -+ v = 2v ^ *2 I .11 : 301 Ji = I 0 rE cm/s x 17,32 cm/s -+ Chgn B. CAu I l. Tirc6ngthirc i==)tD/a,thay tr =clf -+ i:cD/(fa) + Chqn D. Cdu 12. Tg C ktrdng ti6u thu cdng sudt nOn cdng sudt ti€uthp cta do4n m4ch AM li c6ng su6t ti6u thp tr6nbii5ntr0,khitl6tli€ntrdcriabi(introp=,[;a17-2.y=@=40o.T6ng - trd cta mqchZ= J(r+ R)2 + (2, - zr)' :./1zo+40)2 +(60Jt -40Ji)'= 40rEQ + cudng <t0 higu dpng trong mach bing | UIZ : 6Al$0.16) : Ji tZ1t1-r C6ng sudt ti0u thp tr6n dogn mgch AM te p = I2R : (Ji tz'12+0 = 30w-+ vay R:40o; p:30w -+ chgn A. Ctu 13. TrOn mQt ddy ttin h6i, s6ng t6i vi s6ng phin x? ngugc pha nhau t+i dAu c6 ainn chfr khOng phni t4i UAt t<i di6m nio nOn D sai + Chgn D. Cdu 14. Tai thdi <li6m t =Tll}thi cuong tt$ ddng diQn trong mqch bing i = 8cos2nt/T = 8cosn/6 = 4"6mA. Tt c6ng thric (i/ls)2 + (uru0)2: l-) $Jl tqz + (4/tjo)2: l-) hipu tlign th6 cuc ttsi giiia hai bin tU diQn li Uo:8V. Ta c6 CUo2: LIo2 -) L = CUozlti = 5.10-e.82/(8.10r)2:5mH -+ Chgn C. Cdu 15. Tia tri ngopit6c dung l6n cdc lo4i kinh inh n€n cflng tdc dung lOn kinh inh dO chpp inh ban dOm + A dirng. Cdu B vi D dring (SGK VLlz). Tia tti ngo4i cfing tic dung nhiQt -+ C sai -+ Chgn C. CAu 16. Ning luqng c0a m6t xung 5nh s6ng laze W : P.t: I 0.200.1 0-e : 2.10-6J-+ 56 ph6t6n chtia trong mSixung6nhs6ngbingN:W(hcl}.):WV(hc):2.104.0,64.rc-646,625.10-34.3.108;= 6,44J012 h*t-r Chgn A. Cdu l T.Khohngthdi gian ngin nhdt dd vat di tt.UiCn niy dlin bi6n kia bing mQt ntia chu ki dao dQng cria vft chri kh6ng ph6i khoing thdi gian b6t ki -+ C sai -+ Chqn C. C6u 18.TirdiAukiQndAubnitac6phuongtrinhphdnung in* iD-+lT+ jn.N[nglugngmiphin img toi ra lA W: (2mo- m1- mn)c2 : (2.2,0136 - 3,016 - 1,0073)uc2:0,0039.931 = 3,63(MeV). Kh6i lugng nu6c n{ng D2O trong.lkg nu6c tg nhi€n li 0,015%.1000 = 0,159 + sO hgt D2 bing 0,15.6,022.1023n0 : 4,5165.102rhpt. Theo phin ung hat nhdn tr6n thi crir c6 2 hqt Dz thi cho ning lugng 3,63MeV -) t6ng ning lugng thu duo.c bing 4,5165.102t.3,63MeV:1,6395.1022MeV = 1,6395.1022.1,6,10-r3J : 2,624.1OeJ =+ chgn A. Cdu 19. A. M4ch dang c6 cQng hu6rng thi culng tlQ hi€u dgng cria ddng diQn trong m4ch d4t cgc ctgi, khi ting tAn si5 cia ddng tliQn thi cuong ttQ higu dgng ddng diQn trong mach giAm -r A sai. + Chgn A. B. Vi Z tlng n6n hp s6 c6ng su6t cria do4n m4ch gidm + B dfng, C. Khi Tach. c6 c$ng hy*g. s5 chi cia v6n t<ti ti ruong mfc. giira hai ttAu dopn mach g6m tu diQn vi cuSn cim thuAn bing 0, khi tAn sti f thay OOi ttri st5 chi cia v6n kri tang + C rhing. D. Khi cQng huong Zy= Zc, khi tdng f thi ZLtdng, Zg gi6m mi I gi6m -+ Uc : lZg gihm -+ D tlirng. Cdu 20. 6nh sdng don sic khi di tir kh6ng khi vio trong nu6c thi budc s6ng giim ?" : Mn = 0,61(413) = 0,45pm -+ khoing vdn i : ),'Dla: 0,45. rc4.21(0,5.10t') = l,8mm. KhoAng c6ch gifra hai vdn sSng bflc ba tr6n mdn bing 6i = 6.1,8 : l0,8mm -+ Chgn D. CAu 21. ROto cria ttQng co kh6ng tl6ng bQ ba pha ld r6to lOng s6c chf kh6ng phdi ld nam chfrm diQn+ C sai-+ Chon C. Cdu22. D6i trr,rc toa d0 X: x - I = 4cos(srlt+ rcl6) cm. Khi x: -l cm thi X = -2cm. Trong gi6y diu ti€n s6 chu ki bing llT : 110,4 = 2,5it&c li trong 2,5 chu ki dAu tli€m M quay duo. c 2,5 vdng. tvtSi vdng quay, di qua di€m N (c6 X: -2cm, theo chiAu duong) I lAn, trong 2 chu ki M <li qua N .le 2 lAn, cdn l/2 chu ki nta thi M chua qua N, do v4y sti tAn v$t qua tli€m N chi ld 2 + Chqn A. Cdu 23. Trong mpch dao tlQne di€n tir tU do, vu 112 chu ki dao ttQng te tir ktri ddng diQn d4t cgc d4i, n6 lai ttat gi|tri cr,rc dpi n6n ning lugng tir trudng v6n d4t cgc d3i -+ ndng lugng cria mpch dao tlQng t4p trung d cuQn cAm + Chgn A. Cdu 24. Tri thdng cUc Aai qua khung dAy bing Oo: NBS : 50.0,2. 7,8J0-2 = 0,78(Wb). TAn s6 g6c cria tir thdng bing t6c dQ g6c quay cia khung tD: 2nn = 8On(rad/s) -r biAu thirc cria tir th6ng qua khung O : 0,78cos(80rt + n/6)Wb + sudt tliQn tlQng tr€n khung li e: - dQ/dt: 0,78.80nsin(80rt + n/6)Y : l96cos(80nt - n/3) (V) -+ Chgn A. C6u 25. Theo thuy6t lugng trl c6c phdtdn c6 ning lugng e: hf -> c6c ph6t6n c6 tAn s6 kh6c nhau thi c6 n[ng lugng khdc nhau + B sai -+ Chgn B. Cdu26. DOng nlng crla mdi Olectron k*ri dlSn an6t li Wd: eUar: 1,6.10-re.12000: 1,92.10-r5J. 56 Olectron tt6n an6t trong m6i gi6y ln n=lle= 20.10-3(1,6.10-re) = 1,25.1017h4t. 56 electron d6n andttrong 20 phrit li N : n.20.60 = 1.5.1020 hat. NhiQt lugng mi an6t nhgn duo.c li q : 90olNWd = g0%1,5J020J,92.10-rsJ = 2592001 :2s9,2 kJ -; Chgn B. CA.u 27. Trong c6c lo4i tia ph6ng xA thi tia gamma khdng mang diQn, cdn cdc tia cdn l4i mang tliQn tich n€n tia y kh6c vdi cic tia cdn l4i -+ Chqn D. Cdu28. Tai t: 0 (diCm M tr6n duong tron)thi x: 0 -+ dQng nlng cfia vgt dat cuc d4i vd th€ ndng bing 0. Khi l14 ddng ndng chuy6n thdnh th6 ndng thi thd ndng bing ll4 cs n[ng + ll2kxz : ll4.(112)kA' -) x': A2l4 -+ x= -Al2 -+ khoAng thdi gian niy li khodng thoigian v{t tti tri M tttin N tr€n dulng trdn t1,a51 : Tll2: (Znll0n)112: 1160s + Chgn A. Cdu29. Mdy bi6n 6p li m6t thi6t bi ding de Ui'5n aOi diQn 6p cria ddng di€n xoay chiAu vi giir nguydn tAn s6 c0a ddng diQn xoay chi€u n6n A sai + Chgn A. Cdu 30. Trong quang ph6 cfia nguyOn tft hidr6, b6n kinh cria quT dao c6 mftc ndng luqng kich thich thir hai ld 1 ,44a, d6 le ban kinh cria quT d4o M c6 b6n kfnh 9ro-+ b6n kinh Bo bing rs: 1,44a/9 = 0,16a. B6n kinh cria qui dqo c6 mfc ndng lugng kfch thfch thf 4 (qui ttao O) bing 25rs :25.0,16a= 4a -+ Chqn C. C0u 3 l. Chc hgt t4o ra trong m6i phOng x4 li x6c dinh, con c6c hat t4o ra trong nhirng phdn h4ch kh6c nhau cria cDng m6t ddng vi ld khdng x6c dinh. -+ C sai + Chgn C. CAu 32. Ban dAu m4ch cQng huong voi s6ng di€n tir c6 budc s6ng 60m -) Xr : c.2n [LC:60m (1). Khi tdng C th€m 6pF thi budc s6ng )u2= c.2n.JTG+6pn= l20m (D. LaV (2) chia cho (l) -+ (C+6pFyC=4-)C*6:4C-+C=2pF.KhigiimCdi lpFthi diQndungcdnlpFnghialiCgi6mdi mQt nrla, cdn Cl2. Khi tdng L l0n 18 lAn vd diQn dung li Cl2 thl budc s6ng cQng huong ld }4 : c.2n. JISLC I 2 = 3(c.2n.JtC l= 3.60 = l80m + Chgn C. Cdu 33. ChiAu ctia vectcr v{n tdc thay d6i khi'vdt qua vi tri bi6n *r A sai ChiAu cria vecto gia t6c thay d6i lJri vft qua vitrf vi tri c6n bing -+ B sai ChiAu cria lyc ttdn hdi thay d6i khi v|t qua vi tri ld xo kh6ng bitin d4ng -+ D sai ChiAu cria lgc k6o vO thay tl6i ktri vflt qua v!tri cAn bing vi lgc k6o vd lu6n huong vA vi trf cAn bing -> C tlirng + Chgn C. Cdu 34. Di€m M nim trOn vdn cpc ti6u, gita M vi <tuong trung trgc c0a AB c6 2 viln cpc ti€u kh6c -+ M nimtr€n vdn cpc ti€uvdi k=2-+ dz-dr =(2k+ l)M2=(2.2+ l)Llz=37,5-30= 7,5cm -+ 5]"12= 7,5cm-) l. = 3cm -+ S6 Aiem "u, aei ntrGu ntr6t tr0n ttopn itring Oai L trongkhoing gifra A va n iing phin nguy6n cta thuong s6 tt(UZ) cQng th€m L Ta c6 Ll(M2) = 17,25/1,5 = I 1,5 + 56 itiiim cgc tt4i nhiAu nh6t bing 12 -+ Chgn C. Cdu 35. Trdn thang s6ng diQn tir, thti t1r _c6c brtc x4 theo sg tdng dAn cria tAn s6 lar Tia hdng ngopi, tia tri ngopi, tia Ronghen, tia gamma -+ D dirng + Chgn D. C8u 36. fhdi luqng m4t trdi giim cdn mQt n&a, tuc li gi6m tli l030kg. Theo cdng thirc Anhxtanh khdi lugng niy tuong ung vdi ndng luqng E : mc2 : 1030.(3.1 0t)t = 9.1046J -r Khoing thdi gian giam di phAn ndng lugng niy blng t = E/P =9.10461(3,8.1026) =2,386.1020s = 7,51.1012 nlm -+ Chgn B. CAu 37. TAn s6 nh6 nhdt cria 6nh sang kich thich d€ €lectron bft kh6i bA ryt kim loai ld 6 : Aftr = 4,8.1,6.10-rerc,626.10'3a = l,l6.l0r5 Hz-+ EiAu ki€n d6 €lecrron bat kh6i,bd m{t tAm bac li f> l,l6.lOrsHz-+ Chgn A. Cdu 38. Trong hiQn tuqng c$ng huong dao il$ng co, bi6n tlQ dao dQng cu0ng btic tlSt cgc dgi mi tOc AO ti0u hao ning lugng do ma s6t beng t6c dQ cung c6p ning lugng cho h-6.(SGKVLI2) -+ B sai + Chgn B. Cdu 39. Khi ttiQn 6p hiQu dqng hai dAu cuQn cim dpt gia tri cyc tlqi thi tlign 6p hai <tAu tto4n mgch gtim <liQn trd vi tr,r ttiQn ntii titip l$ch pha vdi iliQn 6p hai ttAu do4n mach ld 900 -+ ta c6 gian dd vecto nhu hinh v6. Tir giAn ttd vecto -+ Unc = Jq:fi= ![20t -60' = oor6V; coso = Unc/Ur = AOJi ttZO = .l-l tZ*> cr = nl6 + ug tr6 pha so vdi uns li n/6 + nlz:2n13 -+ pha ban tliu cria iliQn 6p u6 bing nl4 -2n13: -5nll2. O Ta c6 Us = Upscosn/6 = 60\6 .Ji tZ= 90V -+ Bi6u thrtc cria ttiQn 6p hai dAu tp ttiQn li -+ us :9}Jicos(l00nt - 5n/12)Y-+ Chgn C. Ciu 40' Tai nhfrng diiim tr6n vdn ctrc dpi ld chd vdng ggn l6i g?p vdng ggn tOi -+ a dring -+ Chgn A. T4i nhfng ditim tr€n vdn clrc dpi cfrng li ch5 uong gqn l6m g?p vdng gon l6m -+ B sai. Tgi nhirng diiim kh6c nhau tr€n vdn cr.rc dai n6i "nrng pha ld kh6c nhau + c sai. ' T4i nhtrng di0m kh6c nhau tr€n vdn cr,rc ttpi vi vAn cr,rcti6u n6i chung pha li kh6c nhau -+ D sai. Ciu 4l. tchi duu <t6ng ho qu6 l6c tir m4t d6t l€rtniri ruo ooor thi;dg'hd .iiv rrrar ai rai nliy aem ra l,l l8s -+ Ta c6 86400 [o(t" - ta)/2 + h/R] = [,it8 -+ 86400 [2.10-:(h -t^i2 + 0,616400] I i,ilg -> 0,864(tn-to)+8,1 =l,ll8-+(t"-td)o-80c+nhiQtd00mata6t(ta)lonhonnhi6t<lgtr€nniri(tn)li 8oC -+ Chgn C. C6:ll 42. Tia s6ng d6 truyAn trong thuj' tinh c6 budc s6ng tit 0,64/1,6 = 0,4pm dln A,7611,6 : 0,471pm -+ trong thui'tinh tia sdng dd c6 budc s6ng tir 0,4pm ddn A,4751tm. Tia sring ving truyAn ftong ch6n kh6ng c6 budc song tir 0,57pm d6n 0,6pm. Tia s6ng tim truyAn trong nudc c6 budc s6ng tt 0,4 4l(4/3) = 0,33pm diSn 0,38/(413):0,285pm + trong nu6c tia s6ng tim c6 bu6c s6ng tir 0,285prn"dtin 0,331rm. So sdnh c6c k6t qui tr6n ta c6 l.v > ID > l.r -+ Chgn A. (Thi sinh c6 thiS chgn fit n gia tri nio trong i<hodng cric budc s6ng vi thr,rc hiQn c6c phdp tfnh nhu trOn cfing dugc k6t qui cAn tim) Ciu 43. Thi€n HA cria chfng ta c6 dulng kinh bing khodng 100000 nim 6nh s6ng (SGKVLI2)+ C dring -r Chgn C. Cdu 44. Sti hat nhdn !f Co c6 trong I 00g ban ttAu bing No = 100.6 ,022.102316A : 1,A0367 .t O2ahpt. S6 trat B- ph6t ra trong thoi gian t ld No : Noe-r' :2,497.10t7; thay gi6 tri No vd t : I phrit -+ hing s6 ph6ng xg l, =4,146.10-e(lA)-+ s6hatF-sinhratrong I n6m ldn =No-Noe-rt,vdi t= I nim :iAS.z+.leOor- n: 1,23.1023 hat -+ Chgn B. CAu 45. Di6m M nim trdn AB c6ch trung dirlm O cria AB lA 2 cm -+ higu rluong di dz - d1:2.) = 4cm. Vi hai ngudn A vi B ngugc pha nhau n6n bi€n clQ dao ttQng t4i mQt rliem udt ti ii A :l2acos[ n(dz - dr)/1. + nl2ll :l2.Zcosl4nll,2+ nl}ll= l4cos[l tnl61:2Jj" + Chgn C. CAu 46. A. C6ng sudt tiOu thp clign cria do4n m4ch li t6ng cdng sudt ti€u thu tr0n c6c ctign tro thuAn. + A tlfing. B. CuQn cim. thuAn vi tp dign kh6ng tiOu thg cdng su6t. + B rlirng. C. Khi miic nOi tiiSp th6m vio m4ch m6t cuqn cam thuen hlV mOt tu iien thi t6ng r& thay AOi ung ho{c giem tu! thugc gi|tr:i cincim khdng vi dung khang n€n c6ng sudt c0a doan mach c6 th6 ting ho4c giAm. -+C rtung. D. Khi mic ndi ti6p thOm vio m4ch mQt dien tro thuAn thi ilign trd ctia mach ting + tOn! trO ting -r cuong clO hiqu dpng cria ddng tliQn qua mgch gidm -+ cdng sudt cria doqn m4ch cd th6 ting hoac giAm -+ D sai -+ Chgn D. Cdu47. DiQn 6phiQudpnghai dAudo4n mgch bingU = JUtr+(UL-Ur),: ofOd +1tZO-OOy: 60JiV.KhitAns6lif,ta c6ZylR:UlUn:120/60:2;Zc/R:tJclUn:60/60-l.Khitans6lefl2thi Zt':ZJ2;Zc':2k-+ U1'/Up'=Zr-'lR=hJ2R= l-)UL':fJR' ;IJc'/[JR'= k'tR=2ZglR:2) Ug'=2Un].Tirc6ngthfrc(!lpl)2].(Ur'-Uc')2:Ut-(ul')'+(unf=u2-+2(Un')2=u2-r(Un')2: U2/2= 602-+ tliQn dp hai dAu diQn trd bdy giobing Un':60V -+ Chon A. Cdu 48. A. anh sdng tring li h6n hgp cria c6c rinh s6ng don sic c6 miu biiin thi6n li6n tgc tir tl6 d6n tim chft kh6ng phii chirm s6ng g6m c6 biy tia s6ng <ton sic ttr miu dd d6n miu tim -r A sai. B. Mqi rinh sring clon sec mi ta ntrin ttrdy ttAu co bu6c song trong khoang tu chrmg 0,38 pm d6n 0,76 pnr tong ch,6n kh6ng, chf kh6ng phii trong bdt ki m6i truong nio. -+ B sai. C. Khi di tt m6i truong kim chi6t quang sang m6i truong chi6t quang hcm thi chi6t sudt t6ng -+ t6r AO truyAn s6ng gidm + budc s6ng c0a anh s6ng oon s6. giam ai -+ c itring. Vfly chqn C. D. Khi di tir m6i trudng trong su6t niy sang m6i trudng trong sudt khdc, tia sang c6 budc s6ng cang ldn thi chitit sudt c0a m6i trutmg aOi vCi tia s6ng cdng nhd + tia i6ng b! lQch cang 1l D sai Cdu 49. Sau 2 nim mQt lugng ch6t ph6ng x3 gidm tti 4 lin, d6 ld kho6ng thoi gian bing 2 chu ki b6n rd -+ 2T :2ndm -+ Chu ki b6n rd T : lnim + Sau 3 ndm = 3T thi kh6i luqng ch6t ph6ng xa cdn m = mo/23: m0/8, tr?c ld luqng ch6t ph6ng xq cdn lai l/8 lugng ban dAu + Chgn C. Cdu 50' A. MAt trcri ph6t ra quang phO tien tuc vi d6 le kh6i khi c6 6p su6t lon n6ng s6ng ph6t ra -+ A d[ng. B. Quang ph6 cfia m{t troi thu duoc o tnii ddt.li quang phd hdp thu vi 6nh sring m{t trdi khi di qua lop khi quy€n mdt trcri bi lop ndy h6p rhs n€n thu dugc quang phd h6p thg. + B drin!. C. Quang pho trdp thu cria ch6t iong ld quang ptro dam, m5i Oam g6m nhi€u uaitr tt6p thp n6i tidn nhau m6t c6ch li6n tuc -+ C sai -r Chgn C. D. MOt <tdn ph6ng ttiQn chria khf iodng n6n c6 5p su6t thAp, khi phdt s6ng sd phrlt ra quang ph6 vach phrlt x4 -+ D tiling. .Sa,*t6,v, v^f;J\&t't-, . bdt ki m6i truong nio. -+ B sai. C. Khi di tt m6i truong kim chi6 t quang sang m6i truong chi6 t quang hcm thi chi6 t sudt t6ng -+ t6r AO truyAn s6ng gidm + budc s6ng c0a. 1160s + Chgn A. Cdu29. Mdy bi6n 6p li m6t thi6 t bi ding de Ui'5n aOi diQn 6p cria ddng di€n xoay chiAu vi giir nguydn tAn s6 c0a ddng diQn xoay chi u n6n A sai + Chgn A. Cdu 30. Trong. c.2n [LC:60m (1). Khi tdng C th€m 6pF thi budc s6ng )u2= c.2n.JTG+6pn= l20m (D. LaV (2) chia cho (l) -+ (C+6pFyC=4-)C*6:4C-+C=2pF.KhigiimCdi lpFthi diQndungcdnlpFnghialiCgi6mdi mQt nrla,