'Phdn tich vd hic&ng dan gidi
Bai nay giai theo may tinh se cue ky nhanh:
u = i.Z = V2Z0.(10 + 10i-20i) = 2 0 Z - - " '
4 & Vay: u = 20cos Vay: u = 20cos
Chpn dap an A
Bi quySt on luyftt thi aai hqc dat diem toi da Vat It, tap 1 - Le Van Vinh
Chuyto dh 2
B A I T O A N G I A T R I H I ^ U D U N G
^hmmg phdp gidi ' •'' '
Six d u n g cong thuc: = U R + ( U ^ - U c ) haycos(p = — hay U = — - — hay tan(p =
^ ^ U ^ I.cos(p ^ U R
hay dung gian do vec to
ffl V i D U M A U
V l d u 1 : D o n g dien i = 4cos2a)t (A) c6 gia tri hieu d u n g la
A. V 6 A . B. 2 V 2 A . C. ( 2+ V 2 ) A . D . N/2 A .
^hdn tick v>d hic&ng ddn gidi
Q = ji2(t).R.dt=|lg ^i±£25i^f.R.dt 2 ) ^ , v l + cos(4cot) T l + 2.cos(2cot) + ^ ,2p I 4 4 8 = ^ . T = l\, .R.T l\, = ^ = 6 ^ = V 6 A Chpn dao an A
Nhan xet: de'xac dinh cuang do hieu dung cua ddng dien xoay chieu, nguai ta cho
ddng dien xoay chieu va ddng dien khong ddi ciing chqy qua dien tra nao do sau thai gian t giong nhau. Cudi ciing nguai ta do dugc nhiet luang toa ra tren dien tra do trong hai ddng dien tren la bang nhau tie do mai cd khdi niem cuang do ddng dien hieu dung trong ddng dien xoay chieu chinh Id do Ian cua ddng dien khong dot Bdi todn tren, thai gian dugc xet Id mot chu ky cua ddng dien xoay chieu. Day la dang todn tuy de ngan nhung hai mai la ddi vdi nhieu ban vd de thi chinh thuc ciing chua ra thi dang nay.
V l d u 2 : Chpn phat bieu sai? Mach di^n xoay chieu RLC noi tiep c6 R va C
khong doi, dang xay ra cong huong. Ne'u tang L m o t l u g n g nho thi A . dien ap hieu d u n g tren tu di^n giam.
B. dien ap hi^u d u n g tren cuon cam giam C. cong sua't toa nhi^t tren mach giam. D . dign ap higu d u n g tren di^n tra giam.
^hdn tick vd hucmg ddn gidi
Ban dau mach cpng h u o n g nen Z c = Z L => Z = Z^^i^ = R
Cty TNHH MTV DWH Khang Viet
Khi tang R m o t l u g n g nho thi tong tro ciia mgch luc nay: Z = 7 R^ + ( Z L - Z c f t v i Z L - Z c^ O= ^ ( Z L - Z c f > o
U ( - = I Z ( ~ =- ^ r. Z ( ~ => U(-. i ( Z ( - ; U = const) nen A d i i n g R ^ + Z ^
L bien thien de Uimax k h i Z L = — . Ban dau ZQ = Z L nen k h i tang L mot lugng nho thi Z L se tang mot lugng nho v i the U L S B tang va c u tang
R ^ + Z ^
tir t u L den k h i Z L = — - — — thi ULmax v i the trong cau nay di^n ap hi^u
dung tren cugn cam tang nen dap an B sai (adsbygoogle = window.adsbygoogle || []).push({});
P = I ^ R = - ^ y y . R = > P i ( R ; U = const) nen C d i i n g U R = I . R = - ^ . R = > U R i ( R ; U = const) nen D d u n g
Chpn dap an B
v i d u 3: Doan mach A B g o m doan mach A N chua cuon thuan cam noi tiep voi doan mach N B chua dien tro R va tu dien C. Ggi UR, UI,, U C la dien ap hieu d u n g gii>a hai dau m o i phan tir R, L, C. Biet dien ap giUa hai dau A B bien thien dieu hoa vuong pha so v o i di^n ap hai dau N B . H $ thuc nao sau day dung?
A. U ^ + U ^ + U ^ - U ^ = 0 ; R T T2 ^ i TTI _ n ? _ n ."s;
C. U ^ + U ^ + U ^ - U l = 0;
B. U ^ + U ^ + U ^ - U t = 0 ; ' '
D . U | + U ^ + U 2 - U ^ = 0 ;
^hdn tick vd huong ddn gidi Cdc bdi todn velien he giita cdc gia tri hieu dung,
CO mot cdch gidi nhanh, de hieu ma cdc ban can lini
y Id cdch sif dung vecto tritgt da dugc trinh bdy rat chi tiet trong cuon "cam nang luyen thi dai hoc
tap 1" ciia tdc gid nen cdc ban cd thetham khdo.
Tif gia thict decho ta ca gian do vecto trugt:
u^g 1 U N B A A B N vuong tai B A N ^ = AB^ + NB^ o U ^ = U^ + U ^ + U ^ : ^ U^ + U ^ + U ^ - U [ = 0 Chpn dap an B A a. B I
Bi quySi dn luyftt thi dai hpc dat diem tot da V^t It, tap 1-Le Van Vinh
Vi du 4: Mpt doan mach gom di?n tra R, cupn thuan cam L va tu di^n C mac noi tiep (trong do R, L, C la nhung gia trj hiiu han va khac 0). Dat mac noi tiep (trong do R, L, C la nhung gia trj hiiu han va khac 0). Dat
di^n ap xoay chieu c6 gia tri hi^u dung U, tan so i thi thay di#n ap hai
u /s
dau di§n tra R, cupn thuan cam L va ty di^n C Ian lugt UR = ^ ;
U L = y • Khi tan so dong dien la 2f thi di^n ap tren di$n tro, tren tu di^n
va tren cupc cam Ian lugt bang
A . U , = M u , = ^ , U c = U ; B . U , = ^ , U L = V 3 U , U C ^ ^ ; D . U R = U , U L = U , U C = U ;
'Phdn tick vd hizang dan gidi
Tu cong thuc lien he giira cac U:
^2 r.. ^2 , . . . 2 _ . .2 3U^ U L - U C U 2 U 2 L2 ^ 2 Uc =0 Uc = U
Khi tan so tang gap doi: f = 2f:
Z'L = 27tf L = 2ZL U ' L = 2UL = U i _ . ^ = , U c = ^ = ^ i _ . ^ = , U c = ^ = ^
2nfC 2 ^ 2 -
Z'r =•
Ta c6: UR = luon la hang so vi U khong doi nen khi tang tan so len gap doi thi hieu dien the hieu dung hai dau dien tro khong thay doi. gap doi thi hieu dien the hieu dung hai dau dien tro khong thay doi.
Vay chQD dap an C (adsbygoogle = window.adsbygoogle || []).push({});
Vi dlgl 5: Trong mot doan mach xoay chieu AB gom hai doan AN va NB mac noi tiep. Doan AN gom dien tro thuan R mlc noi tiep vai tu C, doan mac noi tiep. Doan AN gom dien tro thuan R mlc noi tiep vai tu C, doan NB chua cuon thuan cam L. Khi mach dang c6 cpng huang, neu sau do chi tang tan so cua dien ap dat vao hai dau doan mach thi ket luan nao
sau day la khong dung?
A. Di^n ap hi^u dung tren doan AN tang.
B. Dien ap hieu dung hai dau dien tro thuan R giam.