A. TM TT NI DUNG V CC PHNG PHP C BN 1. Trng in t

T trng bin thin sinh ra in trng xoy, in trng bin thin sinh ra t trng (xoy). Trong thc t khng bao gi c in trng hay t trng khng i, do in trng v t trng khng bao gi tn ti

c lp

Vi mt in tch, ty theo cch chng ta quan st n (ng yn hay chuyn ng vi n) m ta s quan st thy in trng, t trng theo cch khc nhau. Trong trng hp thng gp ta s quan st thy ng thi

in trng v t trng

C th thy in trng v t trng khng th tch ri nhau, chng ta phi m t chng nh l cc kha cnh ca mt i tng thng nht. i tng gi l in t trng.

2. Sng in t Khi in t trng ti mt im bin ng, bin ng s lan truyn ra xa gi l sng in t. Tm li sng

in t l s lan truyn bin ng in t trng.

Sng in t truyn c trong mi mi trng, n thm ch truyn tt nht v nhanh nht trong mi trng chn khng.

Sng in t l sng ngang: Cc vc t in trng E v t trng vung gc vi phng truyn

Cc vc t E , v v lp thnh mt tam din thun, ngha l nu quay mt chic inh c theo chiu t E n , inh c s tin theo chiu ca v .

3. Thng tin v tuyn bng sng in t

H thng pht sng in t H thng thu sng in t

Cc b phn Chc nng Cc b phn Chc nng

My pht dao ng cao

tn

To ra sng mang (cao

tn) truyn c i xa ng ten thu Thu (nhiu) sng in t

Tn hiu m tn

Tn hiu cn truyn i

c bin i thnh tn

hiu in Mch chn sng

Chn mt sng in t

nh trc theo nguyn l

cng hng

Mch trn sng Gi tn hiu m tn vo

trong sng mang Mch tch sng

Tch tn hiu m tn ra

khi sng mang

Mch khuch i Khuch i tn hiu Mch khuch i Khuch i tn hiu

ng ten pht Pht sng in t Thit b ra

Mang tn hiu n cho

ngi dng (loa, mn

hnh)

BI 16: TRNG V SNG IN T

B. BI TP THC HNH

NI DUNG:

Trng v sng in t ................................................................................................................... 2 H thng pht thu sng ................................................................................................................... 2 Tn s, bc sng .......................................................................................................................... 3 Di tn, di sng ............................................................................................................................ 3 i ton mch ghp ........................................................................................................................ 4 i ton t xoay ............................................................................................................................ 5 Cc bi ton hnh hc ..................................................................................................................... 5

Trng v sng in t Cu 1: (TH - 2009)Pht biu no sau y l sai khi ni v sng in t?

A. Khi sng in t lan truyn, vect cng in trng lun cng phng vi vect cm ng t.

B. Khi sng in t lan truyn, vect cng in trng lun vung gc vi vect cm ng t.

C. Sng in t lan truyn c trong chn khng.

D. Sng in t l sng ngang.

Cu 2: (TH - 2007)Pht biu no sai khi ni v sng in t?

A. Sng in t dng trong thng tin v tuyn gi l sng v tuyn

B. Sng in t l s lan truyn trong khng gian ca in t trng bin thin theo thi gian

C. Trong sng in t, in trng v t trng lun dao ng lch pha nhau

D. Trong sng in t, in trng v t trng bin thin theo thi gian vi cng chu k

Cu 3: (TH - 2012)Khi ni v sng in t, pht biu no sau y l sai?

A. Sng in t mang nng lng.

B. Sng in t tun theo cc quy lut giao thoa, nhiu x.

C. Sng in t l sng ngang.

D. Sng in t khng truyn c trong chn khng.

Cu 4: (TH - 2013)Sng in t c tn s 10 MHz truyn trong chn khng vi bc sng l:

A. 3 m B. 6 m C. 60 m D. 30 m

Cu 5: Trong chn khng mt sng in t c bc sng 100m th tn s ca sng ny l:

A. f = 3(MHz) B. f = 3.108 (Hz) C. f = 12.10

8 (Hz) D. f = 3000(Hz)

Cu 6: (TH - 2008)i vi s lan truyn sng in t th

A. Vect cng in trng E cng phng vi phng truyn sng cn vect cm ng t vung gc vi

vect cng in trng E .

B. Vect cng in trng E v vect cm ng t lun cng phng vi phng truyn sng.

C. Vect cng in trng E v vect cm ng t lun vung gc vi phng truyn sng.

D. Vect cm ng t cng phng vi phng truyn sng cn vect cng in trng E vung gc vi

vect cm ng t . Cu 7: (TH - 2011)Pht biu no sau y l sai khi ni v sng in t?

A. Khi sng in t gp mt phn cch gia hai mi trng th n c th b phn x v khc x.

B. Sng in t truyn c trong chn khng.

C. Sng in t l sng ngang nn n ch truyn c trong cht rn.

D. Trong sng in t th dao ng ca in trng v ca t trng ti mt im lun ng pha vi nhau.

Cu 8: (TH - 2012)Ti H Ni, mt my ang pht sng in t. Xt mt phng truyn c phng thng ng

hng ln. Vo thi im t, ti im M trn phng truyn, vect cm ng t ang c ln cc i v hng v

pha Nam. Khi vect cng in trng c

A. ln cc i v hng v pha Ty. B. ln cc i v hng v pha ng.

C. ln bng khng. D. ln cc i v hng v pha Bc.

H thng pht thu sng Cu 9: Nguyn tc ca mch chn sng trong my thu thanh da trn hin tng:

A. Tch sng B. Giao thoa sng C. Cng hng in D. Sng dng

Cu 10: V tuyn truyn hnh dng sng:

A. Sng cc ngn B. Sng ngn C. Sng trung D. A v B

Cu 11: Sng in t c p dng trong thng tin lin lc di nc thuc loi

A. sng di. B. sng ngn C. sng trung. D. sng cc ngn.

Cu 12: Sng in t no sau y c kh nng xuyn qua tng in li dng trong truyn thng v tinh:

A. Sng trung B. Sng di C. Sng cc ngn D. Sng ngn

Cu 13: Bin iu sng in t l

A. tch sng in t m tn ra khi sng in t cao tn.

B. bin i sng c thnh sng in t.

C. lm cho bin ca sng in t tng ln.

D. trn sng in t m tn vi sng in t cao tn.

Cu 14: Sng in t no sau y c dng trong vic truyn thng tin ra v tr

A. Sng ngn. B. Sng cc ngn. C. Sng trung. D. Sng di.

Cu 15: H thng pht thanh gm:

A. ng ni, dao ng cao tn, bin iu, khuch i cao tn, ngten pht.

B. ng ni, dao ng cao tn, tch sng, khuch i m tn, ngten pht.

C. ng ni, dao ng cao tn, chn sng, khuch i cao tn, ngten pht

D. ng ni, chn sng, tch sng, khuch i m tn, ngten pht.

Cu 16: S ca h thng thu thanh gm:

A. Anten thu, bin iu, chn sng, tch sng, loa

B. Anten thu, chn sng, tch sng, khuch i m tn, loa

C. Anten thu, my pht dao ng cao tn, tch sng, loa

D. Anten thu, chn sng, khuch i cao tn, loa

Cu 17: Hin tng cng hng trong mch LC xy ra cng r nt khi

A. tn s ring ca mch cng ln. B. cun dy c t cm cng ln.

C. in tr thun ca mch cng ln. D. in tr thun ca mch cng nh.

Cu 18: (TH - 2010)Trong thng tin lin lc bng sng v tuyn, ngi ta s dng cch bin iu bin , tc l

lm cho bin ca sng in t cao tn (gi l sng mang) bin thin theo thi gian vi tn s bng tn s ca dao

ng m tn. Cho tn s sng mang l 8 kHz. Khi dao ng m tn c tn s Hz thc hin mt dao ng ton

phn th dao ng cao tn thc hin c s dao ng ton phn l

A. 1600 B. 625 C. 800 D. 1000

Tn s, bc sng Cu 19: Mch dao ng LC ca mt my pht dao ng iu ha L = 2.10

-4 H v C = 2.10

-6 F. c sng ca sng

in t bc x ra l:

A. 37,7m B. = 12,56m C. = 6. 28m D. = 628m

Cu 20: Mch dao ng LC dng pht sng in t c t cm L = 0,25H pht ra di sng c tn s f = 99,9MHz

= MHz. Tnh bc sng in t do mch pht ra v in dung ca mch, vn tc truyn sng c = 3.108 m/s. (

2 =

10).

A. 3m; 10pF B. 0,33m; 1pF C. 3m, 1pF D. 0,33m; 10pF

Cu 21: Mch dao ng ca mt my pht sng in t gm mt cun dy c t cm L = 20 H v mt t in c

in dung C1 = pF. my c th pht ra sng in t c bc sng = 3 m th ta c th:

A. mc song song vi t C1 mt t in c in dung C2 = 60 pF.

B. mc ni tip vi t C1 mt t in c in dung C2 = 180 pF

C. mc ni tip vi t C1 mt t in c in dung C2 = 60 pF.

D. mc song song vi t C1 mt t in c in dung C2 = 180 pF.

Cu 22: Khung dao ng vi t in C v cun dy c t cm L ang dao ng t do. Ngi ta o c in tch

cc i trn mt bn t l Q0 = 106(J) v dng in cc i trong khung I0 = (A). c sng in t cng hng

vi khung c gi tr:

A. 188,5(m) B. 186,2(m) C. 160,5(m) D. 18,4(m)

Di tn, di sng Cu 23: Khung dao ng li vo my thu v tuyn in gm t in c in dung C thay i c t pF n

400pF v cun dy c t cm L = 8H. Ly 2 = 10. My c th thu c sng in t c tn s trong khong

A. 88kHz f 100kHz B. 88kHz f 2,8MHz C. 100kHz f 12,5MHz D. 2,8MHz f 12,5MHz Cu 24: Mch in dao ng bt tn hiu ca mt my thu v tuyn in gm mt cun cm vi t cm bin thin

t 0,1H n 10H v mt t in vi in dung bin thin t pF n 1000pF. Di tn s mch dao ng c th bt

c l:

A. ,59MHz n 159MHz B. , 6 MHz n 126 MHz

C. 59 KHz n 15,9 MHz D. 7,9 MHz n 790 MHz

Cu 25: Mch dao ng chn sng ca mt my thu gm mt cun dy thun cm L bng 0,5mH v t in c in

dung bin i c t pF n 500pF. My thu c th bt c tt c cc sng v tuyn in c gii sng nm trong

khong no?

A. 88,4m n 942m B. 8,85m n 188m C. 6 m n 1680m D. m n 500m

Cu 26: Mch dao ng ca 1 my thu v tuyn in gm 1 cun dy c t cm l L bin thin t 1 H n100

H v 1 t c in dung C bin thin t pF n 500pF. My thu c th bt c nhng sng trong di bc sng:

A. 22,5 m n 533m B. 13,5 m n 421 C. 18,8 m n 421m D. 8,8 m n 625 m

Cu 27: Trong mch chn sng ca mt my thu v tuyn in, b cun cm c t cm thay i t mH n

5mH. mch ch bt c cc sng in t c bc sng t m n 1200m th b t in phi c in dng bin

i t:

A. 4pF n 16pF. B. 4pF n 400pF. C. 6pF n 160nF. D. 4 pF n 160nF.

Cu 28: Mch dao ng ca mt my thu v tuyn gm cun cm thun c t cm bin thin t ,5 H n 10 H

v mt t in c in dung bin thin t pF n 500 pF. My thu c th bt c sng in t c bc sng ln

nht l:

A. 133,3m. B. 233,1m. C. 332,1m. D. 466,4m.

Cu 29: Mt mch chn sng