D. di^n ap hieu dung tren tu giam ,\
A 100/7t Cdch 1: Z c
B. 25/7t |.iF. C. 50/71 nF. , ^ D . 150/n ^F. Huang dan coCj • < Zc2 = 1
CoCn • = 2Z •CI (Pi = + a
(P2 = - a Pl = P2 ^ Z l = Z2 =^ Z L = ^ ^ l i ^ = 1 ,5 Z a
I Theo bai ra: 2a = 7t/2 => a = n/A => tancpi =
. 0 , 5 Z c i 100 > Chon C. = - l = > Z c i = 2 0 0 ( Q ) = > C i = _ Z L - Z a _ R 1 50 = t a n a ) 1 - — . 1 0 " ^ (F) (OZ^I 7t Cdch 2: Z . = ^ C 1+ Z c 2
BO irp men tnae v^t n LMVII umi ncnn VI vj. i^p J. - t-iiu wan n
tan q,, = ^ ^ = - 1 ^ Z c . = 200(Q) ^ C, = = ^ . l O ^ ^ (F)
R 100 w Z ^ i 71 '
V i du 7: Cho doan mach dien xoay chieu RLC nói tiép gom R = 100 [ } , cugn , cam thuan va tu dien c6 d u n g khang Zc thay doị K h i Zc = Zci =100 Q hone ,, khi Zc = Zc2 = 300 Q thi cong suat tieu thu cíia doan mach nhir nhaụ Néu
• cuong do dong dien qua mach khi Zc = Zci la ii = 2 V2 cos(110Ft + K/12) (A) • thl khi ZG = Zc2 dong dien qua mach c6 bieu thiic
• A . i2 = 2 \/2 cos(l lOnt + STT/I2) (A). B. i2 = 2cos(l 1 Orct - 7r/4) (A). C. i2 = 2cos(1107it + 57r/12) (A). D. i2 = 2 V2 cos(l lOTit - T./4) (A).
Huong dan Pi = P2 ^ Z , = Z2 ^ Z L = I = 200(Q) ; Z L - Z r i 1 71 , , , . n ^ - ^ ' ^ t a n q ) i = — ^ = = > ( p , = — => u sdm pha h d n i j l a — R V3 6 6 ^cj,., Zi — Zfo 1 71 . • ^ , , 1V 71 tan(p2 = — — = - —!=•=> = — => I2 sdm pha hdn u la — ^ ^3 , 6 , 6 ,^,.p.^ '2 scim pha hdn ij la ^ QJJv ' ^ ' Qj^f,:. (^Q,
3 a uAiir) <;-- (it) M't:- - ni;):='. .-'j-i--^;-...-'-.
J i2 =272cos(ll07it + — + - ) = 2V2cos(ll07it + — ) ( A ) ^•' . . f l
V • 12 3J \ J ' ,v,5 , ';
' =::>ChonẠ ^ •'^''^ ^ ' V i du 8; Cho doan mach dien xoay chieu RLC noi tiép gom R = 11,7V3 U,
cuon cam thuan va tu dien ccS dien dung C thay doị K h i C = Ci = l/(74 887i) F hoac khi C = C2 = l/(46 807i) F thi cong suat tieu thu cua doan mach nhu nhaụ Biet cuong do dong dien qua mach khi C = Ci la ii = 3 cos(1207tt +
571/12) (A). K h i C = C 3 thi he so cong suát cua doan mach c6 gia tri Ion nhát.
Liic nay, dong dien qua mach CO bieu thiic
Ạ b = 3^cosl207ct (A), i B . i^ = 6cos(1207it + 71/6) (A), '
• <Z.h = 6cos(1207tt + 7t/4) (A). D. i^ = 3 ^3 cos(1207tt + 7./12) (A).
. . - i < Huong dim ,_ ' A , . . „ .:. .-.Sc.o tancpi =• Z, - Z •CI R V3 > = ii6 s6m p h a h d n u l a — 6 .;v-, Z, = 7 R 2+ ( Z L - Z o f =23,4Q ,u = 23,4.3x/3cos 1207it 57t _ 7 I ^ 12 6 = 70,2^3 cos 1207tt + -4 ( V ) ;
K h i cong hUdng • = ^ , = ^ '^os 1207it + -
• 4
( A ) = > C h o n C . ,
Vi du 9: Cho doan mach dien xoay chieu A B khong phan nhanh g o m mot cuon cam thuan, mot tii dien ccS dien d u n g C thay doi dugc, mot di§n tro hoat
dong 100 il. Giira AB co mot dien ap xoay chieu luon on dinh u =
110cos(1207:t - 7c/3) (V). K h i C = 125/(37i) |.iF thi dien ap giira hai dau cuon
cam CO gia trj Ion nhát. Bieu thírc cua dien ap giCfa hai dau cuon cam la Ạ ui = 264cos(1207tt + 7t/6) (V). B. uị = 220cos(1207tt + 71/6) (V).
C. UI, = 220cos(1207rt + 7i/2) (V). D. uị = 110 V 2 cos(1207rt + 7r/2) (V).
/ •••3::^ J - \!; >• '\ '•' Z r = 1 coC = 200Q- , ->Z, = Z r =200=>i = - = l , l c o s (V)nKlu((inK _ R 1 2 0 7 t t - - 3 (A) (200i) = 2 2 0 Z - = 220cos 1207rt + - 6 i(V) =?ChonB.
CMy: Khi C ilmy doi dcso smili cac gin tri I, P, UR, UỊ C6 tlwdung do thi ála chiing theoZc. D\ta vao do thi ta sc thay:
* Zc chng gan Zco thi I, P, UR, UI. cang Ian, ciuig xa thi cnng he (Z^o = Z, );
* L = /2 = / f / n Z c o " = Z L = ^ ^ ^ " Z n + Z r , [Zc3 e( Z c i ; Z c 2) = ^ l 3 > I
-C3 Zci;Zc2 • u<i
V i d u 10: Dat dien ap xoay chieu u = 100 V2 coslOOTit (V) vao hai dau doan mach mac noi tiép gom dien tro thuan R = 50 Q, cuon cam thuan va tu dien
CO d u n g khang Zc thay doị Dieu chinh Zc Ian l u o t bang 15 Q, 50 Q va 45 Q
thi cuang do hieu d u n g qua mach Ian luot bang Ii, I2 va h. Néu Ii = I2 = I thi
Ạ h = 2Ị , B. h < I . C . l 3 = 2 A . D . I 3 > I .
^'^•y , Hu&ugdan
= ^ C ' ^ ^ " = 3 2 , 5 ( Q ) ' ^C34^ci;zc2] . i ^ ^ j " . Chon B.'
V Deso siinh P^ im Pi ta c6 tlwdiing phiivng phnp "giiuig day" nhu saii: Tir P.; I<c duang song song vai true Iwanh day" nhu saii: Tir P.; I<c duang song song vai true Iwanh
1) Détini cong sud't Ian nhd't trong so cac cCmg sud't da cho, ta chi can so sdnh hai gin trigan dinh nhat bang phwang phdp "gidng day". ' *
V i d u 11: Dat dien ap xoay chieu u = UocoslOOTtt (V) vac hai dau doan mach
mac noi tiep gom dien tro thuan R, cuon cam thuan c6 do t u cam 0,25/7t H
va tu dien c6 dung khang Zc thay doị Dieu chinh Zc Ian lugt bang 15Q, 20Q, 29 Q va 50 Q thi cuong do hieu dung qua mach Ian krot bang I i , h, b va
l4. Trong sócac cuong do hieu dung tren gia trj Ion nhat !a *'* '
Ạ I i . ' B. h . C. I3. . . D. I4.
Huang dan
Vj tri dinh: Z(_„ = Z[ = coL = 25(Q)
Cang gain dinh I cang Ion. Vi Zc2 va Zc3 gan Zco hon nen chi can so sanh I2 va I3. Gia trj nao Ion hon se la gia trj Ion nhat trong sócac gia trj da chọ TCr I2 i<e d u o n g song song v o i true hoanh cat do thj tai diem
CO hoanh do Z'l 2 sao cho:
2 2 Vi Z(;3 e(Zt.2;Z'(;2)=> I3 > I2 => Chon C. Vi Z(;3 e(Zt.2;Z'(;2)=> I3 > I2 => Chon C.
V i d u 12: Dat dien ap xoay chieu on dinh vao hai dau doan mach mac nói tiep gom dien tro thuan R = 100 Q, cuon cam thuan c6 do tir cam L va tu dien c6 dien dung C thay doi dugc. Dieu chinh dien dung C de dung khang cua tii bang 100 Q hoac 300 Q tiii cuong do hi§u dung qua mach c6 gia trj bang nhaụ Khi dien ap hieu dung tren tu cue dai thi dung khang ciia tu b5ng Ạ250<:^. B . 7 5 Q . C. lOOVs Q. D . 200 Q.
' *' * Huang dan
I , = I2 + ( Z , - Z c i = + ( Z , - Zc2)- C2 = 2 0 0(Q) 100^ + 200^
200 = 250(n) =>ClionẠ