D. dong dien tire thoi trong mach bang tong cac dong dien tire thoi qua cac p h a n t i r sai vi d o n g d i e n t u c t h o i t r o n g m a c h k h o n g being t o n g cac d o n g
A20072V B 100^/2V C 200V D lOO
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D o u va i v u o n g pha nen ta c6 h$ ( 1 0 0 ^ ^ ( _ 2 ^ ^ ^ 100^ = 1 Giai h? tren ta d u o c U o = 200V C h p n dap an C.
C a u 1 5 : Dat d i ^ n ap xoay chieu u = 220 V2 cos(1007rt) vao 2 dau doan mach g o m dien t r o R = 50Q , cuon cam thuan Z L = lOOQ va t u dien Zc = 50Q mac noi tiep. Trong m o t chu k i khoang thoi gian d i ^ n ap 2 dau mach t h ^ c hien thuc hien cong am la ?
A. 12,5 ms B. 17,5 ms C. 15 ms D. 5 ms
^hdn tick vd hu&ng ddn gidi
C h u k i cua d o n g d i ^ n T = 0,02 (s) = 20 (ms) De dang t i n h du(?c tong tro: Z = 50 Q D p l$ch pha giCra u va i : tancp _ 2 L - Z C _ 1
R => (p= — 4
Bieu thuc cuong d o dong dien qua mach i = 4,4cos(1007:t - j ) (A)
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Bieu thuc t i n h cong suat tuc thai: p = u i = 965 V 2 coslOOTct cos(1007tt - - ) 4 : Dien ap sinh cong am cung cap dien nang cho mach k h i p < 0
hay bieu thuc Y = coslOOTTt cas(1007rt - ^ ) < 0
• Xet dau ciia bieu thuc Y = cosa.cos(a - ^ ) trong m p t chu k i I n
cosa > 0 k h i - — < a < — 2 2 V i i n g phia phai d u o n g th^ng M M ' N c o s ( a - - ) > O k h i - - < a - - < - 4 2 4 2 hay k h i - — < a < — ^ 4 4 , V i i n g phia tren d u o n g thang N N '
} Theo h i n h ve dau cong va dau t r u I o n h o n u n g v o i dau ciia cosa va nho h o n la dau ciia cos(a - ) ta thay v i i n g Y < 0
! k h i cosa va cos(a ) trai dau t u N den M va t u N ' den M ' 4
N h u vay trong m p t chu k i Y < 0 trong t = 2 T T
Do d o trong m p t chu k i , khoang thoi gian d i ^ n ap hai dau doan mach sinh - > 20
cong am cung cap dien nang cho mach bang: — = 5 ms. 4
Bi quye't on luyftt thi dai hgc dat diem toi da Vat It, tap 1 - Le Van Vinh
Chnyta 4