{4, 8,"C, D } (truong hqp 1) md khOng xdt hai trttdng hqp c6 thi'xtb ra.
- Hai li, thltc chdt ddy ld m6r bdi rodn drng hinh nhung kh6ng c6 ban nio clira cdch dung nhimg bO bdn tia nhu the vd khing dinh rang de x6r tar ia cac kha nang
c6 thd duoc Od tao nen c6c bdbon tia d5.
T6m l+, da sd ciic ban mdi chi tidn hdnh c6 m6r rrong bdn bu6c gliri, d6li bu6c phAn tich.
3) Bai to6n nhy dbi hdi phdi s* dung victo (c6c ph6ptoiin tuydn tinh cung nhu ph6p nhAn vO huong). Thieu s6t toiin tuydn tinh cung nhu ph6p nhAn vO huong). Thieu s6t
o phdn 1) s6 anh hudng truc tidp ddn phdn 2)
4) C6cban sau diy c6 ldi giAi t6t hon cd ltuy nhien ddu
thidu phdn trinh biy c6ch dung) : Nguy€n Tuyet Mai,
12A, THPT NK NgO Si LiOn, Bdc Giang ; l.e Bd Long,
10 To6n, THPT chuy0n Hing Vuong, PhtdTho, Phan
AnhTudn,12A1, THPT chuyOn LC Quy DOn, Di Ning,
NGUYEN DANG PHAT
tsei Ll1318"
Clto mdt rnacitc'du di4n trd.nht c'du di4n trd.nht :;o dij birL. d-;ho bi1t:tli =lJfi, h = l4{), }t; = 15,2!2, R,1 -- 39 R. i /i- B ,(:. l4
vdR5 = t}Q. flny tirr I 1" 1,_, !.;, I 1 rd Is klti .
u)! - -t,J,\
bt Uas= 7'l\'.
Ldi giAi. C6 nhidu cdch giiti kh6c nhau (6p
dung dinh luAt Om, 5p dung dinh luAt Ki0c-x6p, 6p dgng phuong ph6p diOn thd nrit, 6p dung
c6ng thrlc chuydn mach tam grdc - sao...).
ThuAn tiOn hon li ding c6ng thrlc chuydn mach tam gi6c sao nhu hinh v6. Ta c5 :
R^ " = Rl - +R, R!R' +R5 = 3,5 (o) ;D - RrRs D - RrRs 1\. - - -:---:- R1 +R2 +R5 = 2,5 (Q) D - RzRs r\D- '- -:---- Rl +R2 +R5__ =4,375(O) Ttd6timduo.cR, =*,n 34 vdR*= T t7 fnl
a) Vdi I =3,4A., dC ddng tim dugc :1, = 1,3 161'
Iz= 1,6 (A) ;1, = 1(A) | I+=2,4 (A) ; 1t = 0,8 (A).
b) Vdi Un=74Y, dC dang tim du-o. c: 1, = 4,5 (A);Iz= 4 (A); \=2,5 (A) ;lo = 6 (A) ) I,=2 (A). Iz= 4 (A); \=2,5 (A) ;lo = 6 (A) ) I,=2 (A).
NhAn x6t. C6c ban sau c6 ldi giAi tdt :
Vinh Phric : Nguydn Xtdn Tudn, 12A4, Nguydn Thi Phuong Dung, lLA3, THPT chuyen Vinh Phric ; Phri
Tho : Ddng Hdng Duy€n, 12H1, TI{PT chuyOn Hing
Vuong ; Bdc Giang : DaogTrung Hi€i,118, THPT NK
NgO Si Licn ; Di NlngzTraong MiltTi€h,11A1, THPT
chuyOn Ir Quy D6n ; Hmg Y6n: Ngd Xudn Dong, 10
Li, TIIPT chuyen Hung Y€n ; Quing Ngai: D6 Nhii
Linh,10 Li, THPT chuydn Le Khidt ; Ddng Nai: Ngrtl'dn
Huy Linh, 11 Lf, THPT chuyen Luong Thd Vinh I Hi
Tinhz Tnrong Tudr Anh. l0 Li. THPT NK Hi TTnh :
Vinh Ph(tc : Drong COng Dinlt, 9/1, TT{PT chuy6n Nguycn Binh Khi0m ; Thanh H6a : Ngu1,,1n Thi Hang, 11T, THPT Lam Son ; Hn Ndi : Biri Phi Anh, 11 Li,
u THPT Ha NOi - Amsterdam, Li Trrh Quyci, 11A3,
TIIPT Nguy0n Tat Thinh ; Dak Ldk :VdThdnlt Ldn,
10C1, THPT NgO Gia Tu, Iakar ; Y€n B6i : llodng\lrt
,R
R,
TruinB, 11H. chuy€n Nguyen Tat Thanh I L4ngSon : li
coni Thiti. l2B, THPT Chu VAn An : Hai uuong :
t't -f,in Ph'in Hai.10A1, TIIPT Kinh MOn ; Bdc Ninh : 'N"r-;71;
st ou.v.1lAl, TIIPT Y€n Phong 1 ; NghQ An :
rj iiea io'n,'ito, t-rtrt Ngma Din; Nsuv€n Quang
iniiii, r ier.nrylNghi Loc t ;vd Dt:tc Quang, trA'
THPTThanh Chuong I :
MAI ANH
Bhi L2l318. Cho hai hbp den X, Y mdc tt6'i
tidp mdi hop chi chua mdr rrong ba pltdn rfr
" R,
L, (cti€n rrd kh1ng ddng ke'), C. Khi m.dc hai Crdm A, M vdo liai cttc ctia mdt ngudn di€n
tnir chi()u thi Io = 2(A), LI"t = 60(V). Kl.ti mitc
Ircti rlidm A, B vdo hqi cilc cia mdt ngudn di€n rtruy chi,u tdn s6'50 (Hz) thi Io= 1(A), U,'1 = 60(V), U,2 = B\(V) vd tts4 ldch pha uv,as ld
120" . Hdi X, Y chita phdn tt? ndo ? Tim'cdc giir tri t'ila chutrg.
Ldi giii. o Vi X cho ddng m6t chidu di qua
rrOn trong X kh6ng chrla tu diOn vh chi chrla R7
vh L,. Theo de bei *, = ?=9 = 30(o).
IA 2
o X6t do?n mach AM khi mac A, B vbo ngudn
xoay chidu : Ta c6 | Z,tu = I = OO (O) =
1
- zLt=10.6(a) - Lt=#
= 0,i7(H). Ngoii ra uN4 sdm pha so v6i i mOt
g5c rp, mh tgq, = +=.6 = Qr = 60o . t\1
o X6t do?n mach MB khi mac A, B vho nguon xoav chidu : Y\ uo,q 10ch Pha so vdi u* g6c
1206, nen c6 thd kei luan ld u*utrO pha so vdi i mot g6c q2 = l2o" - 60o = 60'' Nhu vay I chi c6 thd chrla dicn tr& R, vh tu diOn Cr. Ta cd : Z*u =
8o
= g619; =
r-orL-nLroc %aoff.fr:rTt) giap bia 3;
Nhdn xdt. l) Vien bi phai di tir A ddn C qua
duong ch6o ctra tdtchg o vuOng'
2) buong di dei nha't (khOng. gqn v4t ch6n
n#l
"t u fi-,ot ,ic, bi ld c6c hinh chfr nhAt
uit'r,r,9, (i = 1,2,3,4) (c6chinhchtnhatmd
,lc, ii'aiqua phii giao vdi AC chi tai c6c dinh
O vuOng thu6c AC).
M6i hinh cht nhAt d5 di qua ciic duong ch6o
"t u f A o *ong. Ndu kd ch AC thi chi cdn dlt 4
idm cfr6n thuo; AC vh canh cira 4 hinh chfr nhat iic, ,tj
"O sE di qua duong ch6o cira l8'4 + 9 =
81 6 vuong.
Cdch dit vdt chdn; C5 nhidu cr{ch dit 4 vat
chin (nim ngang holc nam doc) sao cho :
1) C6 it nhA't 1 vAt ch6n nam 6 dinh 6 vu6ng
bOn trong AC.
2) M6i cap hinh cht nhAt MiNiPiQi Q = 1,2'
3. 4) ohii giao nhau o 1 vat chan dd vicn bi phAi
;i ;h;td;"tU hinh chfi nhat nlv qua hinh chfr nhAt kia.
C6c ban sau c6 ldi giAi tdt hon ci duoc nhAn
tang phdm :
tj Nguyen AnhVi€t,12A3, THIrf chuyOn Vinh Phtic
2) Nguy€n Duy Ctl,11A1, THP| Ng6 Gia Tu'
LAp Thach,Vinh Phitc
3) NguyAn Kim Dting,12C, THFrf Tam NOng'
Phri Tho
4) Bni Phi Anh, 11 Li, THP| Ha Noi
Amsterdam, Hn NOi
5) PhamTi€n Vuong,11B11, THP| Binh Son,
Quing Ng6i
6) HodngVdnTuy€n,gA, THCS L0 Van Thinh,
Gia Binh, Bdc Ninh
PHI PHI
. Mat khdc tgqz =
Nhin x6t. Ci4c em c6 ldi giAi gon vh dfng
Hn NOi : Plrum Vi€t Dr:rc, 11A, TIIPT chuyen Li,
DHKHTN - DHQG Hd Nqi ; Ildc Ninh-: Vu YdttTho'
Li lZ, ffryf chuy€n B6c Ninh, Ngtryin-Ba Chuvatt,
iil,i,'n+T Qud"v6 I ; Bdc Giang-: Drong TrLtng
iiai,,'tts, n*'f xr Ngo Si Lien I NghQl\y; DQU
'ttiini
o"iirs,11A3, THPT chuv€n Phan Boi Chau, vinh ,'Ora'nn fri : HodnR Tien'Trung' 12 Toain' THPT
lnJve, -t,e Qri Dour "Phri Tho : Da.ng Hon|. 2uvin'
irrii;-mPr-.huyen Hirng vuons . \y v! n T h i T t d n t r
ttii.'i[s. ]}ryt Ttrantr-Ba ; Thrii B\nh
" Plrum Hd
fii,ri,-tis, TIIPT B6c Duven Hir. Hung H) I Thanh
i;;""r' -u-in- uou, 12A3', THPT Luong D6c -Bing' -Bing'
ii*-n Ho"; 'Hii
Duong: Pham Xuan Thdnh' 42 Chu
Va, Er. to. Hii Duong : Uar tay : Le Vanv4' t'2Al'
fff' pi,Jrg Kh6c Kfr'oan. Th+.t Tt*, D3.1s Nai :
-Phr; ^B;13ri,
tztz, TrIPT Nguven Trai, B,i€n Hba ; Ninh Binh: VaTh!Ngqc Anh' LZA3'TIIPT Yen Kh6nh A'
MAI ANH
tg60" =
Z-
Jt =t. Tu d6 tim duoc : R, = 49 ig)
ve zrr=ayfi(o) = cr=g.rc-' (F) = a6 (pF)n? +Z?i *ZL n? +Z?i *ZL