HU''''ONG DAN QUAN LI su''''DUNG PHtfCiNC PHAP CIAI CAC BAI TAP THI NCHICH VAT LI fli TRtfCiNC TRUNC HOC CCf Sd TS Nguyin Dinh Hung Trudng Cao ddng Hdi Duong Vgt li Trung hpe ca sd (THCS) g^m cdc ph4n CO, n[.]
Trang 1PHtfCiNC PHAP CIAI CAC BAI TAP THI NCHICH VAT LI fli TRtfCiNC TRUNC HOC CCf Sd
TS Nguyin Dinh Hung
Trudng Cao ddng Hdi Duong
Vgt li Trung hpe ca
sd (THCS) g^m cdc
ph4n CO, nhipt, dipn,
quang Ddy la nhihig kidn thiic
\h nhChig hipn tupng ty nhidn
CO bdn, rdt gan gui vd gdn lien
vdi ddi song cua moi HS
Kien thiic vgt li d moi bdi hpe
thudng dupe hinh thdnh thdng
qua 2, 3, 4, thi nghipm Do
dd, vipc dgy hpe Vat li khdng
chi hinh thdnh d HS kidn thiic
khoa hpe vd nhimg hipn tuong
ty nhien, nhihig irng dung kT
thugt ma cdn gdp phdn hinh
thdnh vd phdt tridn d HS nang
luc tu duy, kl nang phan tich,
tdng hpp, k! ndng thyc hdnh
vd kT thugt
Tuy nhien, sdch gido khoa
(SGK) Vgt li, sdch bdi tap vdt
li THCS dii CO nhidu bdi tap
tu dinh tinh ddn dinh lugng
nhung cd rdt it bai tap thi
nghipm vgt li (BTTNVL)
Qua trinh gidi BTTNVL doi
hdi HS thyc hipn mpt chudi
thao tdc tu duy, thyc hanh nhu
chu trinh ciia nhd nghidn ciiu
Vi vdy nd khdng nhiing cd
tdc dyng hinh thanh kidn thiic
mdi, ndng cao chdt lugng ndm
vung kidn thiic ciia HS, hinh
thdnh vd phdt trien d HS nang
luc tu duy, ndng lye thyc hdnh
ma cdn hinh thanh vd phdt
trien 6 HS nhixng kT nang ca
bdn cua nha nghien ciiu
1 Bdi tdp thi nghifm Vat h'
Ngay nhgn bdi 15/12/2012; Ngdy duyel ddng 25/01/2013
BTTNVL Id nhiing bdi tgp vgt li md khi gidi nd ngudi ta phdi phdn tfch, vdn dyng kiln thiic dl ldp lu^n tir dd de xuat mpt thi nghiem vd tiln hanh thi nghipm dd nit ra kdt lugn (dua ra Idi gidi bdi todn)
Co thi chia BTTNVL thdnh:
Bai tgp djnh tinh: Kdt qud Idi gidi cua bai tgp thi nghipm djnh tinh Id sii dyng thi nghiem tao ra mpt sy kipn, mdt hipn tugng vgt li cy the tir
do gidi quyet dupe vdn dd bdi todn ddt ra
- Bdi tgp djnh lugng: Kdt qud Idi giai la nhihig con sd cy the vd phdp do mpt dai lugng vgt li hay sii dyng ket qud ciia phep do cdc dgi lugng vat li dd nghipm Igi mpt cong thiic, mgt dinh luat
- Bdi tgp hpp den cd the coi
Id mpt bai tgp thi nghipm vi khi gidi bdi tgp hpp den ngudi hpe phdi Igp lugn dd dua ra dy doan ve ddi tupng, hien tugng
vd diing thi nghipm dl kidm tra dy dodn
2 Phuffng phdp gidi
BTTNVL
Phuong phdp chung dl gidi mdt BTTNVL cd thi duoc thyc hipn qua bon budc sau:
BI: Tim hilu bdi todn;
B2: Lap lu§n (dl xdc dinh mdi lidn he giiia cac yeu td da cho, phdi tim vd xay dung mdt
phuang dn thi nghiem kiem tra);
B3: Tien hdnh thi'nghiem, thu thgp vd xii li thong tin thu dupe qua thi nghiem; B4: Kit lugn
Vi dy: Cho hidu didn thi U
= 12 V, mpt bdng den 6V, mpt bdng den 4,5V - 4,5W, mpt bien trd, ampe kd, von ke, day noi, khda K
a) Xdc djnh tri so cua cdc phan bien trd, dipn trd ddy tdc moi bdng den vd cong suat cua den 6V khi cdc den sdng binh thudng
b) Cho them mdt dm ke Xdc dinh dipn trd day tdc bdng den khi nd khong dugc mac vao ngudn dien So sdnh vdi kdt qud d cdu a va gidi thich
Birdc I : Tun hidu bdi toan
(tim dii kipn da cho, phdi lim), tdm tdt bai toan
Cho:U = 12V;U„=6V;U^
= 4,5V, Pjj = 4,5 W; bidn trd, vdn
kd, ddy noi, , den sang binh thudng
Tim:
a ) I ^ , ^ M,R.,.,R.«vaP^,
-' lit([roagin^hX' d l ' d2 , dl
b) Rj,, Rj2 bang dm kd khi den khdng dugc c ^ ngudn dien, giai thich ket qua
Birdc 2: Lgp ludn
Mudn tim R^^ ,R^ can do
dugc hipu dien thd ddt vdo hai ddu bidn trd, hipu didn thd dat vao hai ddu ddy toe bdng den sao cho den sdng binh thudng'
Trang 2va cudng dp ddng didn qua
chiing khi dd Ap dyng cdng
thiic: R = U/I ta tinli dugc R
Rieng den D^, do bilt U^, Pj™
nen nlu dilu chinh dl \J^ =
4,5V thi cd thi xac dinh dugc
dien trd ddy tdc den D2 theo
cdng thdc R^ = U^dj/Pj; (Chii
y: Bdi todn khong yeu cdu tinh
theo cdng thiic Do dd viec sir
dyng cdng thiic dd tinh chi de
kilm tra kdt qud do)
Theo bdi ra, dd D,, D^ sdng
binh thudng thi U^, = 6V, U^
= 4,5V Cd thd xdy ra mpt sd
trudng hpp sau:
Ndu mdc Idn lugt timg
den vdo hipu dien the 12V thi
cac den phdi dugc mdc ndi
tilp vdi bidn trd rdi dieu chinh
biln trd sao cho hipu didn thd
giua hai ddu mdi bdng den
bang hieu didn the dinh miic
cua chiing hinh 3)
Hinh 3 So dd mgch dien
thi nghiem do R^ R
Neu hai den mdc ndi
tidp nhau vd mdc vdo hieu dipn
the 12V thi chung phai dupe
mdc ndi tidp vdi nhau qua bidn
trd, dieu chinh bidn trd de U^,,
= 6v, U^ - 4,5V (hinh 4) Tuy
nhien, Idii den D^ sdng binh
thudng thi I^ = I A, khi do I, =
lA vd P, = 6W NghTa Id ndu
den Dj ed cdng sudt djnh muc
khdc 6W thi hai den khdng thd
sdng binh thudng va khdng
the su dung so dd mgch dipn
d hinh 4
Hmh 4 Sa do mgch dien thi nghiem do R^ R^, khi hai den mdc ndi tiep
- Ndu hai den mdc song song nhau xh\ mdc vdo hipu
dipn thi 12V thi chiing phdi dugc mac theo so dd hinh 5
Didu chinh cdc bien trd de hipu dipn thd Uj^, = 6V (hay U-, = 6V),U,, = 4,5V
Tuy nhien, do bai toan chi cho dimg mpt bidn trd ndn khdng the dung so do thi nghiem nhu hinh
5
Hinh 5 So do mgch dien thi nghiem do R^ 7?^^ khi hai den mdc song song
Nhu vdy sau budc lap ludn
GV giiip HS xdc dinh dupe sa
dd maeh didn thi nghiem can sir dyng Id so do cho d hinh 3 (vdi mdi den can tidn hdnh thi nghiem it nhat 3 lan) Budc 3: Tiln hdnh thi nghiem
CJ budc nay, ta tien hdnh cdc Ihao tac sau:
Lya chpn dung cy thich hpp (nhu yeu cdu bdi todn);
Lap bang ghi sd lieu U, I, do dugc;
Ldp rap mgch didn thi nghiem nhu sa dd hinh 3;
Kiem tra su an toan;
Tidn hdnh thf nghiem:
Ddt con hirgt cua bien trd tai vi tri sao cho R^^ cd gid tri eye dai -> ddng khda K -> didu chinh bien Ird (ddng thdi quan sat sd chi cua vdn ke) sao cho U = U^^
-> dpc sd chi cua ampe kd -> ^ i
kit qua U, I do dupe vdo bang
so lieu (tiln hdnh thi nghipm khi mdc ddn 1 vdo mgch dipn rdi 1^ Igi thi nghi^ vdi den 2);
- Ap ( ^ g cdng fliuc tinh U (U
= U^ ± AU), tlnh I a = la, ± AI) vd cdng thirc tinh R (R = U/I), tinh P(P=U.I)
Birdc 4: Ket lugn Phan tich ket qud thi nghiem va nit ra ket lugn: Thi nghipm chung td, khi ddn sdng binh thudng thi
a ) R „ - , R „ =
b) Dimg dm ke do R^ thdy gia tri do dupe nhd hem gid tri xdc dinh dupe trong phdn (a) Gidi thich: Khi ddt vdo hai ddu day tdc bdng den mpt hidu didn thd, cd mdt dong dien chgy qua ddy tdc bdng den, ddy toe bdng den ndng sdng, nhiet dp ddy tdc bdng den cao nen dien trd ciia nd Idn hon khi nd cd nhiet dp phdng (R phy thupc nhiet dp)
3 Mgt s6 bdi tgp thi nghiem phan dien hgc - Vgt li9TBCS
Chiing tdi xin gidi thieu mdt sd bai tap thi nghipm da suu tdm vd xdy dyng sau: 1) Bdng thi nghiem hay chung td rdng cd sy phy thupc lan nhau giiia hidu didn thd d hai ddu mpt doan maeh dien
vd cudng dp ddng dien trong maeh
2) Bdng thi nghiem hay chiing td rdng didn trd day dan phu thudc bdn chdt, kich thudc ciia day
3) Cho cac dien Ord, bdng den, ngudn didn (mpt chidu),
Trang 3khda K, ddy nli Hdy chiing
td rdng:
- Trong mgch dipn gdm cac
dipn trd mdc ndi tiep:
+ Dipn trd tuong duang Idn
ban cdc di^n trd thdnh philn;
+ Cudng dp ddng di§n todn
mgch bdng cudng dp ddng
dipn di qua moi dipn trd;
+ Hipu dipn the hai dau
dogn mgch Idn ban hi^u di^n
the giita hai dau moi dipn trd
- Trong mgch dif n g6m cdc
dipn trd mdc song song:
+ Didn trd tuong duong
nhd hon cac dipn trd thdnh
phdn;
•I- Hieu didn thd hai dau
dogn mgch bang hipu didn the
giiia hai ddu mdi didn trd;
+ Cudng dp ddng dien todn
mgch Idn ban cudng dp ddng
dien qua mdi didn trd
4) Cho ngudn diea (mdt
ehieu), mdt bidn trd, bdng den,
khda K, day ndi Hay chiing to
rdng bien trd Id dipn trd cd tri
sd thay ddi dugc
5) Cho ngudn didn (mdt
ehieu) cd hieu di?n thi thay
ddi dugc, mpt bien h-d, khda K,
didn frd, ddy ndi, cac vdn ke,
ampe ke Hay nghipm Igi dinh
lugt 6m
6) Cho ngudn dipn (mpt
chilu) 4.5V, mpt biln trd, khda
K, cdc day dien trd, day ndi,
vdn kd, ampe kd Hay nghiem
Igi cdng thiic R = p l/S
7) Cho mpt ngudn dien (mpt
ehieu), mdt bien trd, mdt dien
trd, ampe ke, vdn ke, day ndi,
khda K Hay xac dinh tri sd phan
biln trd ndm hong dogn mgch
dipn
8) Cho biln trd, von kl, ampe kl, cdc dipn trd, khda K, ddy ndi vd nguon dipn (mgt chilu) Chiing td rdng cd thi
dimg biln ft-d dk Idm thay dli
hipu di^n thi giiia hai dau mpt dogn mgch di$n vd cudng dp ddng dipn chgy qua m^t dogn mgch dd
9) Cho biln trd, vdn kl, ampe kl, 2 dipn trd, khda K vd nguon dipn (mpt ehieu), ddy ndi Chiing td rdng cd the dimg bien trd dd phan dp, phdn ddng cho mdt doan mgch didn
10) Mpt nguon dien (mpt chidu), mpt day dipn trd cd ehieu ddi AB = 0,5 m, didn
tro suat 1,2 Qm, dudng kinh
0,2mm, day ndi Hay xac dinh dien trd ciia cdc doan AC = 0,15m, AD = 0,25m, AE - 0,4m
vd AB bang ampe ke, von ke va bdng dm kd rdi dimg cdng thiic
R = p l/S de nghipm lai kdt qud
Kit luan
Viec gidi BTTNVL ddi hdi
HS phdi van dyng kidn thiic
dd hpe, sy hieu biet, sy trdi nghidm cimg nhiing pham chat
kT thuat, kT ndng thyc hdnh cua bdn than Viec gidi BTTNVL
se giiip cimg co, khdc sdu kiln thiic, hidu kien thirc Idm cho chat lugng ndm viing kiln thiic dugc ndng cao, giiip hinh thdnh vd phdt triln d HS ndng lye tu duy, tinh can than, ti mi;
hmh thanh vd phat triln d HS ndng luc cimg kT ndng thyc hdnh, kl thugt
Vi vdy, trong qua trinh dgy hpe cung nhu trong kilm
tra ddng gid c ^ phai dua vdo nhung BTTNVL mdt cdch thich hgp
Tdi llfu tham khao
1 Dodn Duy Hinh (chd bidn) Nguyen Van Hda -Ngd Mai Thanh - Nguyen
Due Tham V§t U 9 NXB
Gido dye, H 2010
2 Dodn Duy Hinh (chii bidn) Nguydn Van Hda -Vii Quang - Ngd Mai Thanh
- Nguyen Diic Tham Bdi tdp Vat li 9, NXB Gido dye, H
2010
Summary The laboratory exercises
in physics requires students to apply knowledge leamed, the knowledge, the experience and the technical qualities and skills
of practice itself The laboratory exercises in physics will help strengthen, deepen knowlet^, understanding and knowledge for quality mastering advanced knowledge, help shape and develop in students the capacity to think, the careful meticulous; formation and capacity development in students with practical skills and techniques
Therefore, in the teaching process as well
as in worthwhile checking should be included in physics laboratory exercises properly