TRƯỜNG THCS TÂN BÌNH ĐỀ CƯƠNG ÔN TẬP HKII Họ tên: f2.hcm.edu.vn/data/hcmedu/thcstanbinh/2018_3/de_cuong_ly_7_hkii_17-18... · PDF fileElectron có thể dịch chuyển

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PHN I: L THUYT

Cu 1: C th lm vt b nhim in bng cch no? Vt b nhim in c kh nng g?

C th lm vt b nhim in bng cch c xt.

Cc vt nhim in (vt mang in tch) c kh nng ht cc vt nh khc.

Cu 2: K tn v nu k hiu ca cc loi in tch hc. in tch ca thanh thy tinh khi

c xt vo la, in tch ca thanh nha sm mu khi c xt vo vi kh c qui c nh

th no?

C hai loi in tch: in tch dng (+), in tch m ().

Qui c:

in tch thanh thy tinh khi c xt vo la l in tch dng (+).

in tch thanh nha sm mu khi c xt vo vi kh l in tch m ().

Cu 3: Khi no cc vt nhim in y nhau? Khi no cc vt nhim in ht nhau? Khi no

mt vt s nhim in dng? Khi no mt vt s nhim in m?

Cc vt nhim in cng loi th y nhau.

Cc vt nhim in khc loi th ht nhau.

Mt vt nhim in dng khi mt bt electron.

Mt vt nhim in m khi nhn thm electron.

Cu 4: Trnh by s lc v cu to ca nguyn t.

Nguyn t gm ht nhn gia mang in tch dng, cc electron chuyn ng xung quanh ht nhn to thnh v nguyn t mang in tch m.

Bnh thng nguyn t trung ha v in (ngha l: tng in tch dng ca ht nhn bng tng in tch m ca cc electron).

Electron c th dch chuyn t nguyn t ny sang nguyn t khc, t vt ny sang vt khc.

Cu 5: Ngun in dng lm g? Cho v d mt s ngun in trong i sng. Mi ngun

in u c chung c im l g? iu kin c dng in chy trong mch in l g?

Ngun in dng cung cp dng in cho cc thit b in hot ng. (VD: pin, acquy, cm in, my pht in,...)

c im ca mi ngun in l c u c hai cc: cc dng (+) v cc m ().

iu kin c dng in chy trong mch in: dng in ch chy trong mch kn bao gm cc thit b in c ni lin vi hai cc ca ngun in bng dy in.

TRNG THCS TN BNH CNG N TP HKII

MN: VT L 7

NM HC: 2017 - 2018 H tn:

Lp: 7/

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Cu 6: Dng in l g? Dng in trong kim loi l g?

Dng in: l dng cc in tch dch chuyn c hng.

Dng in trong kim loi: l dng cc electron t do dch chuyn c hng.

Cu 7: Th no l cht dn in, cht cch in? Cho v d vi mi loi.

Cht dn in: l cht cho dng in i qua. (VD: bc, ng, ch, st, nc thng dng,)

Cht cch in: l cht khng cho dng in i qua. (VD: s, nha, g, nc nguyn cht,)

Cu 8: S mch in l g? S mch in c cng dng g? Nu qui c v chiu dng

in trong mch in.

S mch in: l hnh v biu din mch in bng k hiu ca cc b phn mch in.

Cng dng ca s mch in: mch in c m t bng s v t s mch in c th lp thnh mch in tng ng.

Qui c chiu dng in: chiu dng in l chiu t cc dng qua dy dn v cc thit b in ti cc m ca ngun in.

(Lu : Chiu dng in theo qui c ngc li so vi chiu dch chuyn ca cc electron t do

trong kim loi.)

Cu 9: Trnh by v cc tc dng ca dng in. Mi tc dng ca dng in nu mt s ng

dng trong thc t.

Tc dng nhit: dng in i qua mi vt dn thng thng u lm cho vt dn b nng ln, nu vt dn nng ln ti nhit cao th pht sng.

(ng dng trong: Bn i, my sy tc, ni cm in, m in, bng n dy tc,...)

Tc dng pht sng: dng in c th lm pht sng bng n bt th in v n it pht quang (n Led), mc d cc n ny cha nng ti nhit cao.

(ng dng trong: bng n bt th in, n it pht quang (n Led), n bo ca tivi,...)

Tc dng t: dng in c tc dng t v n c th lm quay kim nam chm v ht cc vt bng st, thp.

(ng dng trong: nam chm in, chung in, cn cu dng nam chm in,...)

Tc dng ha hc: dng in c tc dng ha hc, chng hn khi cho dng in chy qua dung dch mui ng th n tch ng ra khi dung dch, to thnh lp ng bm trn thi than

ni vi cc m ca ngun in.

(ng dng trong: k thut xi (m) in cho kim loi, n trang...)

Tc dng sinh l: dng in c tc dng sinh l khi i qua c th ngi v ng vt, gy ra mt s biu hin nh: c co git, tim ngng p, t lit thn kinh,

(ng dng trong: chm cu in, my kch in tim, cc loi my massage vt l tr liu,...)

Cu 10: Cng dng in cho bit iu g? Nu k hiu v n v ca cng dng in.

Cng dng in: cho bit mc mnh, yu ca dng in.

K hiu ca cng dng in l: I

n v ca cng dng in l: ampe (A), miliampe (mA).

1 A = 1000 mA ( mAA x 1000 ) ; 1 mA = 0,001 A ( AmA 1000: )

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Cu 11: Hiu in th c to ra u? Nu k hiu v n v ca hiu in th.

Hiu in th: c to ra gia hai cc ca ngun in.

K hiu ca hiu in th l: U

n v ca hiu in th l: kilvn (kV), vn (V), milivn (mV).

1 kV = 1000 V ( VkV x 1000 ) ; 1 V = 0,001 kV ( kVV 1000: )

1 V = 1000 mV ( mVV x 1000 ) ; 1 mV = 0,001 V ( VmV 1000: )

Cu 12: Mun o cng dng in, o hiu in th phi dng dng c g? Nu cch mc

cc dng c vo trong mch in.

Dng c dng o cng dng in: l ampe k.

Cch mc ampe k vo mch in: mc ampe k ni tip vi vt cn o cng

dng in, sao cho cht (+) ca ampe k ni

vi cc (+) ca ngun in

Dng c dng o hiu in th: l vn k.

Cch mc vn k vo mch in: mc vn k song song vi vt cn o hiu in th,

sao cho cht (+) ca vn k ni vi cc (+)

ca ngun in.

Cu 13: S vn ghi trn mi ngun in cho bit iu g? S vn ghi trn mi dng c in

cho bit iu g?

S vn ghi trn mi ngun in: cho bit gi tr hiu in th gia hai cc ca ngun in khi cha mc vo mch.

(V d: Trn v mt acquy c ghi 12 V, s cho bit hiu in th gia hai cc ca acquy khi

cha mc vo mch l 12 V)

S vn ghi trn mi dng c in: cho bit hiu in th nh mc dng c hot ng bnh thng.

(V d: Trn mt bng n c ghi 220 V, s cho bit hiu in th nh mc bng n

hot ng bnh thng l 220 V)

Cu 14: on mch mc ni tip c nhng c im g?

Trong on mch mc ni tip:

Cng dng in c gi tr bng nhau ti cc v tr khc

nhau ca on mch: I = I1 = I2

Hiu in th gia hai u on mch bng tng cc hiu

in th thnh phn: U = U1 + U2

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PHN II: BI TP.

Bi 1: Bn di cc xe ch xng (du), ngi ta

thng treo mt si dy xch bng st ni thng

xe c cha xng (du) vi mt ng (phn khoanh

trn trong hnh 1). Theo em, ti sao cn phi lm

nh vy?

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Hnh 1

Bi 2: (HKII 08 - 09) Ht nhn trong mt nguyn t canxi c in tch l +20e. V nguyn t

canxi ny c tng in tch l 18e. Nguyn t ny tr thnh ht mang in tch g? V sao?

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Bi 3: Hnh 2 l s cu to n gin ca mt nguyn t.

Hy cho bit:

a/. Nguyn t ny c bao nhiu in tch dng, in tch m?

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b/. Trong nguyn t, ht mang in tch dng c tn gi l g? Ht mang in tch m c tn gi l g?

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Hnh 2

Bi 4: C xt thanh nha sm mu vo mnh vi kh. Hi:

a/. Theo qui c, thanh nha sm mu s b nhim in loi g? Lc ny, thanh nha nhn thm hay mt bt i electron?

b/. Mnh vi kh nhn thm hay mt bt i electron? Lc ny, mnh vi kh s b nhim in loi g?

c/. Electron di chuyn t vt no sang vt no? Thanh nha sm mu v mnh vi kh sau khi c xt nu a li gn nhau th s ht hay y nhau?

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Bi 5: (HKII 10 - 11) Thanh thu tinh sau khi c xt vi la a li gn vt A, th thy thanh thy

tinh b vt A y ra xa. Hi vt A ang nhim in loi g? V sao?

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