lịthíi unijh Jift-ij im 'jtyi ./) Huang dan ^imtii (fb m (Kuril
61 Z L =coL = 2 0 ( Q ) ; Zc = 1 = 10(Q) Zc = 1 = 10(Q)
coC
f^nx « R o = | Z | , - Z e | = 10(Q)
Luc dau R = 20 (Q), roi tang dan tiVi cang ngay cang xa gia tri cue dai nen P
giam dan => Chgn D. "* '"
V i d u 7: Cho mot doan mach RLC c6 R thay doị Dat vaóhai dau doan macin mot dien ap xoay chieu c6 gia tri hieu dung U khong doi va dieu chinh R = .Ro de cong suat tieu thu trcMi nicich dat cue daị Khi do dien ap hieu dung •p tren hai dau ciia R l a 45 V . Tinh dien ap hieu d u n g giua hai dau R khi dieu
' chinh R = 2Rụ
Ạ 56,92 V . B. 5 2 , 9 6 V . C. 6 2 , 5 9 V .
Huong dan
" K h i R = Ro: P,,,, « R „ = | Z , - Z e i = ^ | U , , - U e | = U R „ = 4 5 ( V )
D . 69,52 V .
U = Juf^o + (U, - U c f = 45V2 (V) (Gia tri nay khong thay doi!)
K h i R = 2 R Q ^ J Z L - Z C R 2 nen: 45^2 = U ' ^ + 4 U ' R =18VT0 * 5 6 , 9 2 ( V ) ma = , . U i + ( U ' L - , U ' c r • Chon Ạ
V i d u 8: (DH-20(>8) Dat dien ap u = Uocosait (Uo va io khong doi) vao hai dau
doan mach RLC khong phan nhanh. Biét do tu cam va dien d u n g dugc giu khong doị Dieu chinh tri so dien tro R de cong suat tieu thu cua doan mach dat cue daị K h i do he so cong suat cua doan mcich bang
Ạ 0,85. B. 0,5. . " . <ẹ'L- . • ,r D. l/^/2. ;
&jr.m r r 1 nj- Huong dan . i * '-A ,,>,!;,;.;;.,
Ro _ 1 • C O S (p = R 2 + ( Z L - Z c r J2 • Chon D. Zi - Z r , 7t ta n (p = — ^ = ±1 =>(p = ± - Rn 4 1 =
Luc nay dong dien lech pha so voi dien ap la TI/4. • U U
A )
V R ^ ( Z , , - Z , ) ^ " R O V 5
= 0 + ( U L - U c ) ' => U K „ = |UL - Uc
7 2
V i d u 9: Cho iri^ch dien xoay chieu noi tiép gom bien tro R, cuon day thuan
cam CO cam khang 200 Q va tu dien c6 dung khang 100 Q. Dien ap dat vao
hai dau d o t i n m a c h u = 100 N/2 coslOOnt ( V ) . Xac djnh gia tri ciia bien tro de cong suat tieu thu tren doan mach la 40 W.
Ạ 100 Q hoac 150 Q. B. 100 Q hoac 50 Q. ,t u 0.t • C. 200 Q hole 150 Q. D . 200 Q. hoac 50,Q. ii c,iO ;Ví
. . . | . . . . : . , ^ 1 ff^: fjumig dan \/ Cfc&
P = I^R = U ^ R R 2+ ( Z L - Z c r •40-- lOO^R R^ +100^ R , = 2 0 0 ( Q ) R2 = 5 0 ( Q ) > Chon p . V i d u 10: (DH-2009) Dat dien ap xoay chieu c6 g i a t r i hieu d u n g khong doi vao
hai dau doan mach gom bien tro R mac noi tiép voi tu dien. D u n g khang cua tu dien la 100 Q. K h i dieu chinh R thi tai hai gia trj R i va R2 cong suát tieu thu cua dogn mach nhir nhaụ Biét dien ap hieu d u n g giira hai dau tu dien khi R = R I bang hai Ian dien ap hieu d u n g giua hai dau tu ^ien k h i R = Rz- (adsbygoogle = window.adsbygoogle || []).push({});
Cac gia tri R i va R2 la ."y g f i V i P/> rhn-''-' lif'n Út*^ s.':^''.
'Ạ R i= 5 0 Q , R 2 = 100Q. > ;B. R i = 40 Q, R2 = 250 Q. / ;
C. Ri = 50Q,:R2 = 200Q. • D. R i = 25 Q, R2 = 100 Q.
Huang dan
P = I^R = 4 ^ . R2 - - ! i - R + Z ^ = 0 => R1R2 = Z ^ = 10000
fRi=50(Q) „ , : . , . => => Chon C.
R2 =200(Q)
V i du 11: Mot mach dien gom tu dien C, mot cuon cam thuan L va mot bien tro R dugc mac nói tiep.
Dat vao hai dau mach dien mot di^n ap u = 100 V2 coslOOrtt (V). Khi de bien
tro 6 gia trj Ri hoac R2 thi cong suát tieu thu tren doan mach la nhu nhaụ
Neu Ri + R2 = 100 Q thi gia trj cong suát do bang , 1
Ạ SOW. B. 200W. C. 400W. D. lOOW.