'iA;,'.! i . i i i i i s n ' * 4 . i A i - . . y u t . i , i . U ( . ' . 4 ^ . i i / ^ , '
I ,
1 ^ 1
l/Zị theo kieu ham tam thuc bac 2 nen: = ——* y • ^ R + Z(- ^ R + Z(- Uc = lZc = UZc -11) u VR^.(Z,-Zer |(R^,zf.)J,-2Z,^^^.l , Uc phu thucK
1/Zc theo kieu ham tam thuc bac 2 nen:
1 1 + • + • A n - _ L _ Im ^ = Uc = ịZe = u 1 Zco R' +Z 2 , -72 • U R ' + COL- 1 ^ wC, 2 wC L W - 2 , C ~ 2", 2 . .,2 3 , U c phu c V+ 1 2 ^\ 0^2
thuoc CO- theo kieu ham tam thuc bac 2 nen: = — - —
U , , = 1.ZL = u r.(0L = R^ + (oL - 1 1 1 -2 L_R_^_ C 2 . , U i . phu 1 1 • It , , ^ - 1 CỎ ( 0 , . . n thuoc 1/(0^ theo kieu ham tam thuc bac 2 nen: — = .
Wo 2
Vi du 1: Cho mach dien xoay chieu noi tiep gom cugin day thuan cam c6 do tM cam L thay doi duoc, tu dien c6 dicM-i dung C va dien tro R, Co hai gia cam L thay doi duoc, tu dien c6 dicM-i dung C va dien tro R, Co hai gia
Cty TISHH M T V If V V H Khang Vl^t
khac nhau cua L la Li va L2 thi dien ap hieu dung tren cuon ram c6 cung mot gia trj. Gia tri cua L de dien ap hieu dung tren cuon cam cue dai la mot gia trj. Gia tri cua L de dien ap hieu dung tren cuon cam cue dai la
Ạ L = (Li + L2)»'. L = a5(Li + L2).
C.L = 2 L i L 2/ ( L i + L 2 ) . D. L = L,L2/(Li + L2).
:,,fioi> ' Humgdan :=ic:/ ;
U Z , u
U L = I-ZL = , , — = I 1 ' UL phy thuoc
N / R M ^ T ^ J(R^.Z^).|T2.ZC.^.T
1/Zi theo kieu ham tam thuc bac 2 nen: — = -^Li—5L2. Ln - ^tlll2_
ZLO 2 " L 1 + L 2 =>ChonẠ V ỉ;;..: v ' . . . .-'^ ) , - • ; ; ' i ^ - - :>•. - ^ ' - r , : ^ ;,!,,.!. „';,-,
Vi du 2: Mach dien xoay chieu RLC khong phan nhanh, dung khang bang 50Q, dien tro thuan R va cuon cam thuan c6 cam khang ZL thay doị Nguai ta dien tro thuan R va cuon cam thuan c6 cam khang ZL thay doị Nguai ta nhan thay khi ZL C6 gia tri ung vai 100 Q va 300 Q thi dien ap hi§u dung tren cuc)n cam c6 cung mc)t gia trj. Tinh R.
Ạ 25 Q. B. 19 Q. C. 50 V2 Q. D. 50 Q, Vo •,hm . ) Huaitgdan ,.!) t-,,. j 7 n ? « ''.u <\h 1 m,-^ • U L = I . Z L = ^ ^ ^ = , ^ , U L phu ^ R ^ . ( Z , - Z c f ( R ^ . Z ^ ) . J ^ - 2 . Z c . - l . l ' 1 1 +
thuoc 1/ZL theo kieu ham tam thuc bac 2 nen: = — — ^ = ^ ^ ^
ZLO 2 R^+z^
, = -(100-^ + 300"' ] => R = 5072 (f^) ^ Chon C. R2+502 2^ ^ V / . R2+502 2^ ^ V / .
Vi du 3: (DH-2009) Dat dien ap xoay chieu u = Uocoscot c6 Uo khong doi va co
thay doi dugc vao hai dau doan mach c6 R, L, C mac nói tiep. Thay doi (o
thi cuong do dong dien hieu dung trong mach khi co = coi bang cuong do dong dien hieu dung trong mach khi co = C02. He thiic dung la : dong dien hieu dung trong mach khi co = C02. He thiic dung la :
Ạ (COI+co2)LC = 2. B. coia)2LC = l .
C. (coi + co2)2LC = 4. D. (coi+(02)2LC = l . .
Huang dan »- , (adsbygoogle = window.adsbygoogle || []).push({});
Cdch 1: I = — = , ^ , I phu thuoc co theo kieu ham phan thuc
z rr^ ^ y • • y
r
R2 + c o L - coC,
nen: COQ = ^C0jC02 = . / — - CO1CO2LC = 1 => Chon B.
• hí!:-
Afi f r v ;
LC
fs«'ifif/,»*/«••«/.'!/«• r.ie ii i/rim i i t - n h i - i i h í'.ff//, t.>i, .." •« i m van Bien
Cdch 2: \
I khong thay doi => Z khong thay doi
2 / . N2
o)iL 1 = R2 + (02L - 1 • © 1 0 ) 2 = 1
V i d y 4: M o t mach xoay chieu RLC noi tiep chi c6 tan so f dong dien thay doi duoc. K h i f = 12,5 H z va f = 50 H z thi cong suat tieu thu ciia mach nhu ' nhaụ Thay doi f sao cho cong suat toan mach Ion nhát thi trong thoi gian 1
s CO bao nhieu Ian cuong do dong dien qua mach bang 0?
Ạ 50. B.15. C.25. D. 75.
P = T R = U^R R2 + R2 +
t::m coL- (oC
^ , P phu thuQC CO theo kieu ham phan thuc nen:
COQ = sjo3i(i)2 '-=> i = yjtj^ - 2 5 ( H z ) . Trong 1 chu k i dong dien = 0 hai Ian, ina
trong 1 s CO 25 chu ki nen so Ian dong dien = 0 la 2x25 = 50 Ian = v Chon Ạ
V i d u 5: (DH-2011) Dat dien ap xoay chieu u = Uocoscot (Uo khong doi va ro thay doi dugc) vao hai dau doan mach gom dien tra thuan R, cuon cam
thuan CO do t u cam L va tu dien c6 dien d u n g C mac noi tiep, " o i CR^ < 2L.
Khi (0 = 0)1 hoac co = 002 thi dien ap hieu d u n g giira hai ban tu dien c6 cung m o t gia trj. K h i o) = coo thi dien ap hieu dung giCra hai ban tu dien dat cue daị He thuc lien he giiia coi, C02 va coo la
Ạ cOo = i ( c O ] + C 0 2 ) . C. COQ = 4^x^2 • B. 0)g D. = i ( c o ? + c o i ) . «0 1 1 + 'A) Huang dan U- U r - I . Z r =• coC U V R2 + coL - coC L2C V- 2 L C R ' 2 2\ =--,Ucphu I
thuoc theo kieu ham tarn thuc bac 2 nen: COQ = => Chon B.
V i dv 6: M o t mach di^n xoay chieu noi tiep gom cuon cam va t u di#n c6 dien
d u n g C thay doị D u n g von ke c6 di^n tra rat Ian mac vao hai dau tu dien-
Thay doi C nguoi ta thay k h i C = 40 jiF va C = 20 yiF t h i von ke chi cung trj
só. T i m C de von ke chi gia trj cue daị (adsbygoogle = window.adsbygoogle || []).push({});
Ạ20|aF. B. 10).iF. C. 30 ^F. D . 60 ^iF.
Ctr T/VtfHMTVDVVHKhaiig Vift U r Huang dan U V R^ . (Z , - Z C) ^ | {R 2 . Z ^ ) J^ - - 2Z, - ; - . 1 , Uc p h i ! thuoc 1/Zc
theo kieu ham tarn thuc bac 2 nen:
C = ^ ^ ^ ^ = 30(|.iF) ^ Clion B.
1 ^ Z c i _ ZL
>2 r,2
^CO
V i d u 7: Dat mot dien ap xoay chieu u = Uocos(1007Tt) V vao doan mach RLC c6
R = 100\/2 cuon cam thuan c6 do t u cam L < l,5/7t H va tu dien c6 dien dung C thay doi dugc. K h i dien dung tu dien Ian lugt la Ci = 25/TT (|aF) va
C2 = 125/(37i) ((.iF) thi dien ap hieu d u n g tren tu c6 ciing gia trj. De dien ap
hieu d u n g tren dien t r a R dat cue dai thi gia trj cua C la
Ạ50/TT(^F). B. 200/(371) (|.iF). C. 20/7T (^F). D. lOO/rt (^F). Huatig dan Zci = - ^ = 400(Q);Zc2 = ^ - = 240(Q) coCi CoCn Ur = U Z r u ^ R2 + (Z L - Z C) ' | ( R2 +Z M - V- 2Z L- ^ - + 1 f "-'zl ' Z c •, Uc phu thuoc 1/Zc
theo kieu ham tarn thuc bac 2 nen: 1 _ Zci ZQ2 _ Z,
^CO 2 R2 +Z L ZL =100(Q) ' ' ,áJ ZL =100(Q) ' ' ,áJ 2 T^J.'. R2 + Z ? 300 UK = max o Zc = ZL = 100 => C = 1 100 C o Z r 71 (|.iF) =:>ChonD. . .... í: V Í:.:. Hụ:.^^^ Chuy:
^) Khi C thay doi dc so sanh cac gid tri Uc c6 the diing do thi \JQ- ^ diing do thi \JQ- ^
( R2 +Z M 4 - 2Z L - ^ + 1
^ ^'Zl: ^Zc
theo ZQ . Dm vao do thi ta se thay:
* ZQ canggan ZQQ thi Uc cang Ian, cangxa thi cang be (Zco = cang be (Zco =
Bo trp kien thiic V$t li LTDH tren hcnh VTV2, t^p 2 - Chu V.in BlSn
z +z
UcA = Uc2 = Uc thi Z'X = — —
Z c 3 e ( Z c l ; Z c ' 2) = > U c 3> U c =>Uc3 - U c
1) Dc so sank Ua va Ua ta c6 the dung phmrng plidp "gidng day" nhw sau: Tit Uc, kc duvng song song vai true hodnh neu Ua trcn day thi Ua > Uc, va néu duvi dai/ kc duvng song song vai true hodnh neu Ua trcn day thi Ua > Uc, va néu duvi dai/ tin Ua<Ucị : V^r^': _
3) Dctlni Uc Ian nhat trong socdc cong suat đ cho, ta clii ciin so sdnh hai gid tri gan
dinh nhat bang phuvng phdp "gidng day".
V i du 8: Dat dien ap xoay chieu vao hai dau doan mach noi tiep goin dien tro,
cuon cam thuan va tu dien c6 d u n g khang Z c thay ctoị Goi Ucm.iv la gia trj
sv? cue dai cua dien ap hieu d u n g tren tụ Dieu chinh Z c Ian i u g t b a n g 50 Q, I S O ftv Q va TOO Q thi ctien ap hieu d u n g tren tu Ian lugt bang U i i, Uc2 va U c i . Néu
'^t^ U c i = Uc2 = a thi (adsbygoogle = window.adsbygoogle || []).push({});
A . Uc3 = U c n i a x . B. Uc3 > ạ C. Uc3 < ạ D. U c - = 0,5Ucn,r,x.
Huang dan
Uc, = Uc2 « Zco = = - 0,0133 * Zl\ 0,01 Ụ-a ^ U
Zc', =50^' =0,02 =150^' =0,0067
ụH'>
• ZQT^ nam trong ^
Z c 2 ; Z a) => > U ^ . Chon B.
V i du 9: Dat dien ap xoay chieu 220 V - 50 H z vao hai dau doan mach noi tie])
gom dien tro 50 il, cupn cam thuan c6 cam khang 100 i1 va tu dien c6 dung khang Zc thay doị Dieu chinh Zc Ian krgt bang 50 Q, 100 il, 150 Q va 200 Q
thi dien ap hieu d u n g tren tu Ian lugt bang Uci, Uc2, Uc3 va Uc4. Trong so
cac dien ap hieu d u n g noi tren gia tri Idn nhát la
A . Ucị B. Uc2. C. UC3. D. Uc4. Humgdan Zci =50"' =0,02 =100"' =0,01 =150"' =0,0067 Zc'4 =200"' =0,005 • = 125"'Q« 0,008 7-' 7-' yri
Ta nhan thay, cang gan d i n h Uc cang Ion. va Z^^^^ gan dinh hon nen chi
' ' " c a n so sanh U^., va U(^3 . T u Uc2 ke d u o n g song song voi true hoanh, eat do
thj tai d i e m t h u hai CO hpanh do Z't^'j dugc xac d j n h :
182 7-1 Zco - + Z ' -1 C 2 100"' + Z c ' 2 .125"' = . Z c 2 =0,006 f At) ,
^ Z o nam trong (z'e2;Zc;'2) =^ ^(^3 Wn hrfn Chon C.
Vi du 10: (DH-2011) Lan lugt dat cac dien ap xoay chieu ui = U V2 cos(1007i:t +
(pi); U2 = U V2 cos(l 207rt + 92) va u i = U ^2 cos(l 107tt + 93) vao hai dau doan
mach gom dien tro thuan R, cugn cam thuan c6 do t u cam L "a tu dien c6
ctien d u n g C mic noi tiep thi cuong do dong dien trong doan mach c6 bieu
thuc t u o n g u n g la: ii = IN/2 cos(1007rt); i2 = IV 2 cos(120Trt + 27x/3) va h =
r V2 cos(n07:t - 2Tt/3). So sanh I va Y, ta c6: A . I = r. • B . I = r N/ 2 . C . K I ' . ..J'^ ' Huoiigdiin U Do thi 1 = theo (0 coL - 1 D . I > i ' . 1* ífJ 1 C O dang n h u h i n h vẹ Cang gan vj
tri dinh dong hieu d u n g cang Ion nen I ' > I
= > C h g n C . ""^ .
Vi du 11: Doan mach noi tiep g o m dien tro, tu dien c6 dien d u n g 0,l/7i mF va
cugn c a m thuan c6 do t u c a m l/n H . Néu dat m o t trong cac uien ap xoay chieu sau day vao hai dau doan mach tren thi cuong do hieu d u n g trong mach Ion nhát l i n g voi dien ap naỏ
Ạ u = U()Cos(105Kt) V. B. u = Uocos(857it) V • « ' C . u = U()COs(957it)V. ..^^^ D. u = Uocos(707rt) V
Vj t r i d i n h : WQ = ^ 1
Ta nhan tháy, cang gan vj tri dinh I cang Ion, vi (adsbygoogle = window.adsbygoogle || []).push({});
vay, ta chi can so sanh hai gia tri gan dinh nhat va nam hai ben dinh la (O3 = 957t rad/s va
tt)4 = 10571 rad/s . Tif I3 ke d u o n g song song v o i true hoanh cat do thi tai diem t h u hai c6 hoanh do co'3 duge xac d i n h n h u sau:
cO(^=ff)3Có3 =:>(1007t)^ = 957ta)'3 :^co'3 « 1 0 5 , 3 7 t ( r a d / s ) . •
Huang dan
• = 1007t(rnd/s)
. c
Bo trff kicn thiic V^t li LTDH tren kenh VTV2. t^p 2 - Chu V0n BiSn
V i W4 e [ c o 3 ; a ) ' 3 ] n e n I 4 > I 3 = > C h o n A .
Chu y: Mot so hai todn kc't hap) diéu kien cue dqi va do lech phạ
V i du 12: Dat dien ap xoay chieu vao hai dau doan mach A B nol tiep g o m dien
tro R, cuon day cam thuan L va t u dien c6 dien d u n g C thay doi dimẹ Khj
C = Ci thi dong dien tre pha 7i/4 so voi di^n ap hai dau doan mach.
Khi C = Ci/6,25 thi dien ap hieu d u n g giua hai tu cue daị T i n h he so cong
•K suát mach A l i k h i dọ •.•;.!}:•;;,,;.•• • i - . " . ^ . , A . 0,6. , „ , 5.0,7. C. 0,8.
Huong dan
C = C i =>tan(p5 = tan — ZQI = ZL - R 4 C = 6,25 R ^ - Z c 2 = 6 , 2 5 Z c i = 6 , 2 5 ( Z L - R ) D. 0,9: u C m a x C O S ( p = <=>Zc2 = R^ + Z 2 2 2 L ^ 6 , 2 5 ( Z L - R ) = ^ ^ i^ = > Z L = 4R R R V R ' + { Z L - Z C2 ) ' =r = 0,8 ^ C h o n C . =^Zc2 = 25R 12 R2 + UR 25R V 3 12
V i du 13: Dat dien ap xoay chieu vao hai dau doan mach A B nol tiep g o m dien
tro R, cuon day cam thuan L = 2/n H va t u dien c6 dien d u n g C thay do!
'' dugc. K h i C = Ci = 0,l/7i mF thi dong dien tre pha 7t/4 so v o i dien ap hai dau doan mach. K h i C = Ci/2,5 thi dien ap hieu d u n g giira hai t u cue daị Tinh * tan só goc ciia d o n g dien.
' A . 2007t rad/s. B. 50n rad/s. C. IOOTI rad/s.
Humgd^n
* C = C i =:>tan(pi = ^ t - ^ 5 £ i = t a n | ^ R = Z L - Z c i
D. 107t rad/s.
C = ^ = ^ Z c 2= 2, 5 Z a
U, C m a x 0 Z c 2 = ( Z L - Z C I ) + Z 2
- 2 ^ râLCi = 2 111- = 2 => CO = IOOTI(rad/s) =5 Chon C.
Z c j ' Tt 7t
Chii y: Khi R khong dot va hai gid tri cua L hoac C hoac co ma I, P, UR khong thay dot
„ „ R R
tht Z ] = Z2 = = > C O S ( p i = COS(P2 (p2 = - a (adsbygoogle = window.adsbygoogle || []).push({});
Dong dim trong hai truvng hap lech pha nhau la lạ
CtyTNHHMTVDVVHKhang Vift
V i du 14: Doan mach RLC dat d u o i dien ap xoay chieu o n d i n h c6 tan so f thay
doi dúoc. K h i tan so la fi va l<hi tan so la h thi pha ban dau ciia d o n g dien
qua mach la -71/6 va 7t/3, con cuong do hieu d u n g khong thay doị T i n h he
socong sualt mach khi f = fỉ
C A . 0,5. B.0,71. C.0,87. D . 0,6.
Hudngđn ^ 5 .., ,
I i = I2 =^ Z l = Z 2 =^ • • coscp^ = cos 92 9 ] = ~92
Dong dien trong hai t r u o n g hop lech pha nhau la 2a = —
3 • a = •
• Chon B.
V i du 15: Mach xoay chieu nol tiep g o m cuon day thuan cam L, dien t r o
R = I50V3 Q va tu dien C. Dat vao hai dau doan mach hieu dien the u =Uocos27Tft (V) v o i f thay doi dirgẹ K h i f = fi = 25 H z hay f = f2 = 100 H z thi dong dien trong mach c6 gia tri hieu d u n g n h u nhau n h u n g lech pha nhau 2TC/3. Cam khang cua cuon day k h i f = fi la
Ạ 600Q. B. 150Q. C. 300 Q. • D . 450 a
Huang dan
1 1 _ T _ 7 W2 I j = I2 => Z j = Z2 COi032 = • I j = I2 => Z j = Z2 COi032 = •
LC (OjC
Dong dien trong hai trirang hgp lech pha nhau la CO, 2a = 271 • a = • co,L- tancpj = • —s ^ cpi = 3 —»' ^ 3 (P2 = 3 1
cojC ZLI - Z Ll CO2
CO1 _ V 3 = ^ L I ( 1 L 4 ) ^ 2 L I = 1 5 0 ( Q )
R ^ ^R, .\ J. 150V3
=>ChonB. :
Chii y: Chung ta co thechmig minh aic cong thuc giai nhanh sau day:
* Khi R thay dot hai gid tri Li vd L2 md co ciing P tin Pmax khi: RQ = ^^1^2 •
Khi L thay doi hai gid tri L l vd L l md
CO Cling 1, Uc, UR, P tht Lnax, Ucmax, URnmx, Pmax khv. Lg = ^ . >v'í' ^ '
CO 2 L L
3 Cling UL thi Uiimx khi: LQ = - — ^ — ^ .
L l + L2 (adsbygoogle = window.adsbygoogle || []).push({});
B d trp ki£n thiic V^t It L TBIl tren kSnh VTV2. t^p 2 - Chu VSn Bicn
CO Cling I, UL, UR, P thi Imax, Ulnmx, L/KIHIIA, Pmax khị C ( ) =
C 1 + C 2
CO Cling Uc till Ucm.u khi: C Q = 2 Q C 2 C , + C 2
Khi CO thai/ doi hai gid tri MI va coi nih
CO Cimg I, UK, P th'l hu,ix, Unmax, Pmax khi: Ci)(, = ,yo)|Ci)2 .
2 2 .1 • - . •
CO Cling Uc thi Ucmx khi: O)Q = ^ " ^ .
* CO Cling Ul. thi Uijiiax kiii: li^Q = . • ;,,
2 • • ~ .,.
4. c o t h a y d o i . - ... u S u b w o / f ! u f i l / . ; ? r
rt. ft; ihay doi lien qiian dcu dien dp liieii dung.
Bdi todn: M o t doaii mach dien xoay chieu gom dien tro thuan R , cuon day thuan cam (cam thuan) c6 do tu cam L va tu dien c6 dien d u n g C mac noi tiep. Dat vao hai dau docin mach tren mot dien ap xoay chieu ma chi c6 tan so goc (0 la thay doi duoc. T i m co de dien ap hieu d u n g tren tu cue dai (Uc) hoac tren cuon cam cue dai (Ui).
* Dieu kien dien dp hieu dung tren tu, tren cuon cam cue daị
Dat = L goi la tro tọ
Vc 2
Dinh UBHDl: K
1) Uc = max « Z L = Z,. ("C max L to") £ 2 ) U L = max o Zc = Z,. ("L max => C tó) ^
, '•} <t
u
CMl: Uc = I.Zc = • (i)C = max
R ^ + (oL 1 coC. L _ R ^ b_ 2a =-t> (oL = , — - CMl: U L = I . Z L =• U(oL U R 2 + (oL - (oC - 2 L _ R C 2 2 A = = r = max 1 : + 1 2, 7 -CO 186
CtyTIVtHMrv I > VIII l i h a n g VIfit
b ^ 1 C 2_ 2a co-^ 1 coC
Dat Z \ , L
0phjiBHD2: osi;) ivv;4 O H iv.;vi úl/;!' '.rnit; \ífấi•'ir . . . i M w ' yv]'-.] j' ^ y j '
= u . ^ = ụ-c_
RZ',
C M ;
L R^ (adsbygoogle = window.adsbygoogle || []).push({});