dat vao dien ap xoay chieu co bieu thuc u = 282cos314t (V). Lap bieu thiic cuong do tuc thoi cua dong dien trong doan mach.
^hdn tich m huang ddn gidi
Tansogoc: co = 2Trf = In.SO = lOOn rad/s Cam khang: Z L = coL = 10071.64.10"^ « 20Q
D u n g khang: ZQ = ^
coC 10071.40.10 - 6 * 8 0 Q
T o n g t r o : Z = ^R^+ ( Z L -Z^f = JsO^ + (20 - 80)^ = lOOQ
Cuong do dong dien cue dai: I^, = U„ 282 = 2,82 A
Z 100
Do lech pha ciia hieu dien the so voi cuong do dong d i ^ n :
Z L - Zc _ 20 - 80 _ 3 R " 80 ~ 4 R " 80 ~ 4 tancp = •(p*-37° ' 9 i = 9 u - 9 = - 9 = 3 7 " = 3771 Vay i = 2,82 cos 314t + 180 3771 ^ rad; 180 (A)
Cau 7: M o t doan mach gom cuon cam c6 do t u cam L va dien tro thuan r mac noi tiep voi tu dien c6 dien dung C thay doi duoc. Dat vao hai dau mach mot hieu dien the xoay chieu c6 gia trj hieu dung U va tan s o f khong doi. Khi dieu chinh de dien dung cua tu d i ^ n c6 gia trj C = C i thi dien ap hieu dung giOa hai dau tu dien va hai dau cupn cam c6 cung gia trj va bang U,
cuong do dong dien trong mach khi do c6 bieu thuc ij =2V6co6 1007rt+- (A).
Khi dieu chinh de dien dung cua tu dien c6 gia trj C = C 2 thi dien ap hieu dung giua hai ban tu d i f n dat gia tri cvrc dai. Cuong dp dong d i ^ n tuc thoi trong mach khi do c6 bieu thuc la
A. i2=2V2cos(1007rt + 57t/12)(A) B. i2 = 2^cos(1007tt + 7t/3)(A)
C. i2=2V3cos(1007rt + 57r/12)(A) D. i2 = 2^/3cos(1007tt + 7t/2)(A)
<Phdn tich v>d huang ddn gidi
Khi C = Ci => U L = U c = U (cong huong) => U R = U = U L = U c ^ R = Z L
= 9 i i = 7
Cuong do dong dien cue dai: lo, = Y " =
Khi C = C 2 ^ U c n , a x ZC2 =
Z^ + R ^ _ R ^ + R ^ _ R = 2R R = 2R
D Q l?ch pha gii>a u va i luc nay: tancpj = Z , -Zc2 R - 2 R , 7t
R
7t 71 7t 7t
^'2 M^" 4 4 4 2
Ma (p2 =(Pu -cpi2 = - - :
Cuong do cue dai trong truong hop nay la: , Uo Uo _ Uo ^02 - • R R Un 2V6 ^ + ( Z L- Z c 2 f ^
Vay bieu thuc cuong do dong dien trong truong hop C = C 2 :
= 2V3A
h = 2V3COS 1007rt + -
2,
Chpn dap an D
Cau 8: Dat dien ap u = 100 N/2 COS 1 0 0 7 t t - -
2 (V) vao hai dau mot doan mach 25,._2,
gom mot cuon cam c6 dien tro thuan r = 5Q va do t u cam L = —10 H mac noi tiep voi mot d i f n tro thuan R = 20Q. Bieu thuc cuong do dong di?n trong doan mach la
A. i = 2^/2 cos(1007Tt - n/4 ) (A). B. i = 4 cos(1007it + 7i/4) (A).
C. i = 4cos(1007it-37r/4)(A). D. i = 2N/2 cos(1007rt + 7i/4) (A).
^hdn tich vd huang ddn gidi
25.
Cam khang: Z L = wL = I O O T I . —1 0 " ^ = 25Q
7t
Do lech pha giua u va i : tancp = 25
R + r 20 + 5 = 1: .cp = -
It 71 3n
Ma (p = cpu - (Pi ^ cPi = (Pu - ^ = ^2 ~4
Cuang do cue dai: IQ = 7(R + rf + Zl 725^+252 Un 100^/2 = 4A Vay bieu thuc cuong do dong di^n trong truong hg-p C = : Vay bieu thuc cuong do dong di^n trong truong hg-p C = :
3TV
i = 4cos 100-Kt--
Chpn dap an C
Cau 9: Dat dien ap xoay chieu u = 100>/2 coscot (V), co thay doi dugc dat
vao hai dau doan mach AB gom hai doan mach AM va MB mac noi tiep. Doan mach AM gom bien tro mac noi tiep vol cupn cam thuan, doan mach Doan mach AM gom bien tro mac noi tiep vol cupn cam thuan, doan mach
MB chi CO mot tu dien. Khi co - 1007i(rad/s) thi dien ap hieu dungU^,^,
khong phu thuoc vao gia tri cua bien tro, dong thai dien ap hi^u dung
UMB =100V. Khi A. u^M =100V2cos A. u^M =100V2cos C. UAM =100^2 COS 1007tt + - 3 3 (V). B. UAM=200COS (V). D. UAM =100V2cos 1007rt + -3 ( V ) . 6 (V).
^hdn tich m huang dan gidi
Hieu dien the hieu dung hai dau AM:
AM - V R 2 + ( Z L - Z c f I Z C ( Z C - 2 Z L )
Theo bai ra: UAM « R O ZC - 2ZL = 0 ZC = 2ZL => UL - ^ = ^
Ta lai c6: UR = ^Ju^ -{\Jj^-Vcf = ^100^ -(50-100)^ = 50V3V
=> U A M = V U R + = ^(soVs)^ + 50^ = lOOV
U L - U C 50-100
= 50V
Dp Ipch pha giiJa u va 1: tancp = Ma (p = (pu - (Pi =^ (Pi = cp^, - (p = 0 - Ma (p = (pu - (Pi =^ (Pi = cp^, - (p = 0 -
I 6
50V3 " V 3 ^ ^ ~ 6
71
6
, . U L 50
tJo lech pha giua UAM va i: tan(pAM = — = U K " 5 0 V 3 ~ V 3 ^ ^ ^ ^ ^ f
Cty TNHH MTV nV\lI Khtmg Viet
Ma <PAM ='PUAM ^
Vay: UAM =100N/2COS
71 TT T:
6 6 1007lt + - V 1007lt + - V
Chpn dap an A « ' >
CaU 10: Doan mach dien xoay chieu AMB cau tao gom doan AM chua R va C mac noi tiep voi doan MB chua cupn cam thuan c6 L thay doi. Dien ap C mac noi tiep voi doan MB chua cupn cam thuan c6 L thay doi. Dien ap xoay chieu hai dau mach AB: u = 7572cos( lOOTit+^] (V). Dieu chinh L den
V 2 J
khi UMB C6 gia tri cue dai bang 125 V. Bieu thuc dien ap giua hai dau AM la A. u,,M= lOOcosflOOTit +^1 (V) A. u,,M= lOOcosflOOTit +^1 (V)
C. UAM^IOO^^'-'OS SoOnt--^ 2,
B. UAM= 100V2cosl00Tit (V) (V) D. U A M = lOOcoslOOnt(V) (V) D. U A M = lOOcoslOOnt(V)
'Phdn tich vd huang dan gidi