Vdy chon dap an B... Vay chgn dap an B.. Vay chgn dap an C... Vay chpn dap an A.. Vqy chgn dap an C.. Dieu chinh dien dung cua t u dien de dien ap hieu dung giuTa hai ban tu dien dat g
Trang 1Cdu 36: D a t dien ap xoay chieu u = u V 2 c o s l 0 0 7 i t vao h a i dau doan
mach m^c noi tiep gom dien trd t h u a n R, t u dien c6 dien dung C va
cuon cam t h u a n c6 do tiX cam L thay doi difcfc Dieu c h i n h L de dien ap
dai do bkng 100 V va dien ap hieu dung d hai dau t u dien bang 36 V
A 64 V B 80 V C 48 V D 136 V
G i a t
K h i dieu chinh L de dien ap hieu dung of hai dau cuon cam dat gia
U ^ = U ^ + ( U , - U e ) '
S u y r a : U = ^V^{V^-Vc) ^ ^m{\00-26) = S0 (V)
Vay chgn dap an B
Cdu 37: M o t chat diem dao dong dieu hoa t r e n true Ox vdri bien do 10cm, chu k i 2s Moc the nang d v i t r i can bkng Toe dp t r u n g b i n h cua
chat diem trong khoang thcfi gian ngan n h a t k h i chat diem d i tCf v i t r i
the nang la:
A 26,12 cm/s B 21,96 em/s
C 7,32 cm/s D 14,64 em/s
G i a i
T h d i gian ng^n n h a t vat d i tCf v i t r i c6
dong nang b^ng 3 Ian the nang de'n v i t r i
ta CO the bieu dien nhiT t r e n h i n h ben
TCf h i n h ve suy ra:
^> = - = nt^t=-{s)
v = 5 ( > / 3 - l ) 6 = 21,96(cm/s)
Vdy chon dap an B
123
Trang 2Cdu 38:
K
hi no
i v
e tia
y , phat bie
u na
o sa
u da
y
sa i?
A.
T ia
Y
CO
k ha
nkng da
m xuye
n ma nh horn t ia
X
B.
T ia
y kh on
g ph
ai l
a son
g die
n tiT
C Ti
a y
C O
t an
so Idf
n hcf
n t an
so cu
a t ia
X
D Ti
a y k ho ng mang dien
Giai
Tia
y
la
m
ot son
g die
n tC
f c
6 bifd
c son
g r
at nga
n nh
o hor
n 10
"^^m
Vay chgn dap an
B
Cdu 39:
T ro ng t
hi nghie
m Y-an
g v
e gia
o tho
a an
h sang , kh
e he
p S
phat r
a don
g thof
i b a
buTc
xa dcto sS
c c
6 hiidc
song la X,,
=0,42n
,m,
A,2
=0,56^m va
>.3=0,63|im
Tr en m an , tron
g khoan
g giOf
a ha
i va
n
sang lie
n tie
p c
6 ma
u gion
g ma
u va
n tr un
g t am , ne
u h
ai va
n san
g cu
a
ha
i buf
c x
a tr ijn
g nha
u ta chi tin
h l
a mo
t va
n san
g th
i s
o
va
n sdn
g
quan
s at
diftfc la :
A 27 B 26
C 21
D 23
Giai
Ta co : X , : A.^
: =
6 :
8 :9
Vi tr
i t ru ng nhau
3 v an ufng vdfi :
kX
= kjX
j
k,}., =
^ 6k , = Skj =
9k =
72n
Ti nh ra k ,=
12
,
k2
=9
,
k3
=6
So
va
n t
ru ng la boi cu
a cap :
(6, 8 ) = 24; 48 , 72
; (6 , 9 ) = 18; 36
; 54 , 72
; (8 , 9 ) :
= 72
To ng
so va
n qua
n sat
: 1
2 +
9 + 6
- 8 = 21
Vay chgn dap an
C
Cdu 40:
H ie
n ti/gfn
g quan
g die
n ngoa
i l
a hie
n tifgrn
g electro
n
bi hur
t r
a
"khoi ta
m k im loai kh
i
A.
chieu vao t am k im loai na
y mo
t buf
c x
a die
n tii
c6 bifdr
c son
g
th ic
h htfp
B.
cho don
g die
n cha
y qu
a t am k im loai nay
C t am
im
loai na
y
bi nun
g non
g bd
i mo
t nguo
n nh ie
t
D.
chieu vao ta
m k im loai na
y m6
t chu
m ha
t n ha
n h eli
Trang 3Giai
Hien tifgrng quang dien ngoai la hien Wtfng electron b i buft ra khoi
tarn k i m loai k h i chieu vao tarn k i m loai nay mot buTc xa dien tCr c6
budfc song thich htfp
Vay chpn dap an A
Cdu 41: Mach dao dong dien tCr LC gom mot cuon day c6 do t\i cam
50mH va tu dien c6 dien dung 5 |x F Neu mach c6 dien trcf thuan 10"^ Q ,
de duy t r i dao dOng trong mach vdi hieu dien the ciic dai giiJa hai ban
tu dien la 12V t h i phai cung cap cho mach mot cong suat trung binh bang
Giai
T a c o r i u ^ ^ l c U ^
Cong suat cap bu: P = - I ^ R = - - U ^ R = 72.10^ W = 72pW
Vqy chgn dap an C
Cdu 42: Dat dien ap xoay chieu u = UN/2 coslOOTit ( U khong doi, t t i n h
bang s) vao hai dau doan mach mSc noi tiep gom" dien trof thuan R,
cuon cam thuan c6 do tU cam — H va tu dien c6 dien dung C thay doi
57t di/oc Dieu chinh dien dung cua t u dien de dien ap hieu dung giuTa hai ban tu dien dat gia t r i cifc dai Gia t r i ciic dai do bang uV3 Dien t r d
R bang:
A 2 0 Q B 10N/2Q C 2 O V 2 Q D l O Q
Giai
Ta c6: Z L = (o.L = 2 0 Q
U c „ = - ^ ^ ^ ^ ^ ^ = = = ^ R = ^ = loVSn
Vqy chgn dap an B
Cdu 43: M o t con lac dcfn dang dao dong dieu hoa v6i bien do goc ao
tai nofi c6 gia toe trong triTcfng la g Biet lire cang day lorn nhat bang
1,02 Ian liic cang 6ky nho nhat Gia t r i cua tto la:
A 6,6° B 3,3^ C 9,6° D 5,6°
1 2 5