Chitsanzo cha Mafunso Okambirana za Magnetism
Magnetism ndi chinthu chofunikira kwambiri komanso chosangalatsa chachilengedwe chomwe chiyenera kuphunziridwa mu fizikisi. Chochitikachi chikugwirizana ndi mphamvu zomwe zimachitika pakati pa maginito ndi zinthu zina. Kawirikawiri, maginito amatha kufotokozedwa kudzera m'malingaliro a maginito, mizere ya mphamvu yamaginito, komanso kuyanjana pakati pa maginito ndi maginito ndi zinthu za ferromagnetic, paramagnetic, ndi diamagnetic. M'nkhaniyi, tikambirana zitsanzo zingapo za mavuto ndi zokambirana zawo zokhudzana ndi mutu wa maginito.
Funso 1: Kuzindikira Mizati ya Maginito
Funso: Magineti ya bar ili ndi ndodo ziwiri, ndodo yakumpoto ndi ndodo yakum'mwera. Fotokozani momwe mungadziwire ndodo za bar magnet pogwiritsa ntchito kampasi.
Kukambirana:
Kuti mudziwe mitengo ya maginito a bar, gwiritsani ntchito kampasi. Nazi njira izi:
1. Ikani kampasi pafupi ndi mapeto ena a bala la maginito.
2. Yang'anani singano ya kampasi yomwe imasonyeza kumpoto ndi kum'mwera.
3. Ndodo ya maginito yomwe imakoka mbali yakumpoto ya singano ya kampasi ndi ndodo yakum'mwera ya maginito, chifukwa ndodo yakumpoto ya singano ya kampasi (yomwe kwenikweni ndi ndodo yakum'mwera ya maginito ya kampasi) imakokedwa ndi ndodo yakum'mwera ya maginito.
4. Mofananamo, sunthani kampasi kumapeto ena a maginito opingasa ndipo bwerezani zomwe mwawonazo. Mapeto a maginito omwe amakoka nsonga ya kum'mwera kwa singano ya kampasi ndi nsonga yakumpoto ya maginito, chifukwa nsonga yakumpoto ya singano ya kampasi imakokedwa ndi nsonga yakum'mwera ya maginito.
Funso Lachiwiri: Mphamvu ya Maginito Yozungulira Waya Wolunjika Wonyamula Mphamvu
Funso: Waya wautali wowongoka umanyamula magetsi a 5 A. Dziwani komwe mphamvu ya maginito imalowera mozungulira wayayo pamalo okwana 10 cm kuchokera pa wayayo.
Kukambirana:
Mphamvu ya maginito yozungulira waya wowongoka imatha kudziwika pogwiritsa ntchito lamulo la dzanja lamanja. Umu ndi momwe mungachitire:
1. Gwirani waya ndi dzanja lanu lamanja, ndi chala chanu chachikulu chikuonetsa komwe mphamvu ikuyenda (kuchokera ku zabwino kupita ku zoipa).
2. Kulunjika kwa masipoko ozungulira waya kumasonyeza komwe mphamvu ya maginito imalowera.
Mwachitsanzo, ngati mphamvu yamagetsi yalunjika mmwamba (monga chala chachikulu), ndiye kuti pamalo 10 cm kuchokera pa waya, mphamvu ya maginito idzazungulira motsatira kayendetsedwe ka chala chakumanja:
– Ngati mfundo ili patsogolo pa waya, mphamvu ya maginito imaloza mkati (ku pepala/chinsalu).
– Ngati mfundo ili kumbuyo kwa waya, mphamvu ya maginito imaloza kunja (kuchokera pa pepala/chinsalu).
Funso 3: Mphamvu ya Lorentz pa Tinthu Tomwe Tili ndi Mphamvu ya Mphamvu
Funso: Tinthu tating'onoting'ono tomwe timayatsidwa (+1.6 × 10^-19 C) tikuyenda pa liwiro la 2 × 10^6 m/s timalowa mu mphamvu ya maginito ya 0.01 T yolunjika kunja kuchokera patsamba. Dziwani kukula ndi komwe mphamvu ya Lorentz yomwe tinthu tating'onoting'ono timakumana nayo.
Kukambirana:
Mphamvu ya Lorentz pa tinthu tomwe timayatsidwa mu mphamvu ya maginito imatha kufotokozedwa ndi equation \( \vec{F} = q \vec{v} \times \vec{B} \).
– Kulipira tinthu tating'onoting'ono, \(q\) = +1.6 × 10^-19 C
– Liwiro la tinthu, \( \vec{v} \) = 2 × 10^6 m/s (kuganiziridwa kuti kuli ku x-axis)
– Mphamvu ya maginito, \( \vec{B} \) = 0.01 T (kunja kwa tsamba, kupita ku z-axis)
Kuti mudziwe malangizo a mphamvu:
1. Gwiritsaninso ntchito lamulo la dzanja lamanja kuti mudutse veketolo ya liwiro (\( \vec{v} \)) ndi mphamvu ya maginito (\( \vec{B} \)).
2. Zala za dzanja lamanja zimatsatira njira ya liwiro (x-axis), pindani zalazo kupita kunja kwa pepala (malinga ndi mphamvu ya maginito ya z-axis), kenako chala chachikulu chimapereka njira ya mphamvu ya Lorentz (y-axis).
Kukula kwa mphamvu ya Lorentz \( F \) kungawerengedwe motere:
\[ F = q \cdot v \cdot B \cdot \sin \theta \]
Popeza \( \theta \) = 90° (liwiro lolunjika ku mphamvu ya maginito),
\[ F = (1.6 \nthawi 10^{-19} C) \cdot (2 \nthawi 10^6 m/s) \cdot (0.01 T) \sin (90°) \]
\[ F = 3.2 \nthawi 10^{-21} N \]
Kulunjika kwa mphamvu kumatengera kupindika kwa chala (kumanja = positive y-axis).
Funso 4: Mphamvu ya Magnetic Pakati pa Solenoid
Funso: Zimadziwika kuti solenoid yayitali imakhala ndi ma turn 500 okhala ndi kutalika kwa 0.5 m yokhala ndi mphamvu ya 2 A. Werengani kukula kwa mphamvu ya maginito pakati pa solenoid.
Kukambirana:
Mphamvu ya maginito mkati mwa solenoid yayitali ikhoza kuwerengedwa pogwiritsa ntchito njira iyi:
\[ B = \mu_0 n I \]
Kumene:
– \( B \): kukula kwa mphamvu ya maginito mkati mwa solenoid (Tesla)
– \( \mu_0 \): vacuum permeability coefficient (\(4 \pi \times 10^{-7} \: T \cdot m/A\))
– \( n \): chiwerengero cha ma turns pa unit length (ma turns/meter), opangidwa ngati \( n = \frac{N}{L} \)
– \( I \): kuchuluka kwa mphamvu yamagetsi yomwe ikuyenda kudzera mu solenoid (Amperes)
Kotero,
– \( N = 500 \)
– \( L = 0.5 m \)
– \( n = \frac{500}{0.5} = 1000 \: kutembenuka/m \)
– \( Ine = 2 A \)
Choncho,
\[ B = \mu_0 \cdot n \cdot I \]
\[ B = (4 \pi \times 10^{-7} T \cdot m/A) \cdot (1000 \: kutembenukira/m) \cdot 2 A \]
\[ B = 8 \pi \nthawi 10^{-4} T \]
\[ B \pafupifupi 2.51 \nthawi 10^{-3} T \]
Funso 5: Kuyambitsa Magetsi a Magetsi
Funso: Chokokera chimakhala ndi ma turns 200 ndipo chimayikidwa mu mphamvu ya maginito yomwe imasintha kuchoka pa 0.1 T kufika pa 0.5 T mu masekondi 0.25. Werengani mphamvu yamagetsi yomwe imachokera mu chokokeracho.
Kukambirana:
Kulowetsa kwa ma electromagnetic kumatha kuwerengedwa pogwiritsa ntchito lamulo la Faraday:
\[ \ masamu{E} = -N \frac{\Delta \Phi_B}{\Delta t} \]
Dimana,
– \( \mathcal{E} \): mphamvu yamagetsi yoyambitsidwa (Volts)
– \( N \): chiwerengero cha matembenuzidwe
– \( \Delta \Phi_B \): kusintha kwa maginito flux (Wb)
– \( \Delta t \): kusintha kwa nthawi (nthawi)
Ndi \(\Delta \Phi_B = B \cdot A \); komwe A ndi dera la coil. Komabe, ngati dera silikusintha
\[ \mathcal{E} = -N \cdot \frac{\Delta B \cdot A}{\Delta t} \]
Popeza \(\Delta B = 0.5 T – 0.1 T = 0.4 T \),
Maka
\[ \mathcal{E} = -200 \cdot \frac{0.4 T \cdot A}{0.25 s} \]
\[ \ masamu{E} = -320 \cdot A \]
Ngati palibe malo enieni omwe aperekedwa (omwe akuganiziridwa kuti ndi ofanana),
Mtengo wa induction umadalira pa A.
Tikukhulupirira kuti zitsanzo izi za mavuto a maginito zikuthandizani kumvetsetsa malingaliro ndi momwe maginito amagwiritsidwira ntchito. Malingaliro ndi mfundozi zimagwiritsidwa ntchito nthawi zonse pamaphunziro osiyanasiyana komanso mu kafukufuku wozama.
