Z, - Z p 100 - 200 , n .
DQlgchpha: tancp= \ =-1 =^cp = - - r a d
Pha ban dau cua cuong do dong dien :
(p = (p^ -(pj ^(Pi =(p^-(p = 0 + ^ = ^rad
Bieu thuc hi^u dien the: i = 2,2cos
Chpn dap an C 1007tt + -4J (A)
Vl d u 3 : Cho mach dien A B , trong do C = ;^1037:"' ' 271' " F , L = r_1_ ^ H , R = 25n
mic noi tiep. Bieu thiic di^n ap giiia hai dau mach U^B = 50 %/2 cos 1007:tV. Viet bieu thuc cuong dp dong dien trong mach ? Viet bieu thuc cuong dp dong dien trong mach ?
A. i = 2cos C. i = 2cos C. i = 2cos 1007lt-- 4 1007lt + - 4J A A B. i = 2N/2COS D. i = 1,272COS 1007tt-- 4j A. 1007it--6
'Phdn tich vd huang dan gidi
Cam khang: Z L = L.co = —I O O T I = 50Q .
271 Dung khang: ZQ = Dung khang: ZQ = '^•^ 1007.. ^-^o ,-4 = 75n 371 Tong tro: Z = V r ^ + ( Z L- Z c ) ' = ^(25)^ + (50 - 75)^ = 2572Q. UQ
Cuong dp dong di^n cue dai: lo = = 2A
Z, - Z r 50-75 , n ,
Ctu I Mil I MIVDWHKhang Viit
UR = - = ^[eOsflf -60^ = 60V
Cuang do dong dien cue dai: \Q = -5^^ = ^^'^
R 30 = 272A
Dp I^ch pha giiJa u vdi i: tancp = ^ = — = l=>(p = -=>(Pi=(p^,-(p = - - Z^ = iL
UR 60 4 3 4 12
Vay: i = 2V2cos
Chqn dap an A
1007tt + — 12J 12J
Vl d u 8 : Cho ba linh ki^n R = 60Q, cupn day thuan cam L, tu di^n C. Lan luot dat dien ap xoay chieu c6 gia tri hi?u dung U va tan so f khong doi luot dat dien ap xoay chieu c6 gia tri hi?u dung U va tan so f khong doi vao hai dau doan mach noi tiep RL hoac R C thi dong di^n qua mach c6 cac bieu thuc ii = V2 cos(100nt - ) (A) va i2 = V2 cos(100TTt + ^ ) (A). Neu dat di^n ap tren vao doan mach RLC noi tiep thi dong di^n qua mach CO bieu thuc:
A.i = 2cos(100nt+ -)(A).
3
C i = 2 V 2 c o s(1007Tt+ -)(A).
3
B. i = 2cos(100Tit + - ) (A).
4
D. i = 2V2cos(100TTt+ - )(A)
4
(Phdn tick v>d hudng dan gidi
Theo bai ra ta c6: IQI = I02 => Zi = Z2 \I^^+Zl = JR^TZJ => Z L =
tan(pi - tan(p2 = R
Z L - Z C
• tancp] = -tan(p2 =>(Pi = -92
Trong do: (p,; (p2 la do l^ch pha ciia di^n ap 2 dau mach voi i^; ij
_n 7n
Tudo (D,^1 ^'1 =0),, -cpi, = 4 — I-f-—1 I2J 3 3 = —rad=>(P2 = - ^ r a d tancpi = % = ^/3 ZL = 60>/3Q R tancpi = % = ^/3 ZL = 60>/3Q R
Vi ZL; Z(~ la cac h3ng so ma Z ^ = ZQ nen khi dat di^n ap tren vao mach
RLC noi tiep thi hi^n tugng cgng huong xay ra nen Z = R va u cung pha voi i. Do do cuang dp dong di^n eye dai trong mach: Do do cuang dp dong di^n eye dai trong mach:
Bi quyet on luy$n thi dai hQc dat diem toi da Vat It, tap I - Le Van Vinh
u = 100N/2 cos(wt + -) iV), thi khi do di|n ap hai dau di#n tra thuan c6 4
bieu thuc UR=100cos(o)t) (V). Bieu thuc di#n ap giua hai dau cupn cam thuan se la thuan se la
A. U L = 100cos(wt+ - ) ( V ) .