Laʻana o nā Nīnau Kūkākūkā Magnetism
He mea nui a hoihoi loa ka Magnetism i ke aʻo ʻana i ka physics. Pili kēia hanana i nā mana e kū nei ma waena o nā magnet a me kekahi mau mea. Ma keʻano laulā, hiki ke wehewehe ʻia ka magnetism ma o nā manaʻo o nā kahua magnetic, nā laina magnetic o ka ikaika, a me nā pilina ma waena o nā magnet a me nā magnet me nā mea ferromagnetic, paramagnetic, a me diamagnetic. Ma kēia ʻatikala, e kūkākūkā mākou i kekahi mau pilikia hoʻohālike a me kā lākou mau kūkākūkā e pili ana i ke kumuhana o ka magnetism.
Nīnau 1: Ke ʻike ʻana i nā pou Magnetic
Nīnau: ʻElua mau pou o ka makeneka pā, kahi pou ʻākau a me kahi pou hema. E wehewehe pehea e ʻike ai i nā pou o kahi makeneka pā me ka hoʻohana ʻana i ka panana.
Kūkākūkā:
No ka ʻike ʻana i nā pou o kahi magnet bar, e hoʻohana i ka panana. Eia nā ʻanuʻu:
1. E kau i ka panana kokoke i kekahi wēlau o ka pā magnet.
2. E nānā i ke kui panana e hōʻike ana i ka ʻākau a me ke kūkulu hema.
3. ʻO ka pou makeneka e huki ana i ka ʻaoʻao ʻākau o ke kui panana ʻo ia ka pou hema o ka makeneka, no ka mea, ua huki ʻia ka pou ʻākau o ke kui panana (ʻo ia hoʻi ka pou hema o ka makeneka panana) e ka pou hema o ka makeneka.
4. Ma ke ʻano like, e hoʻoneʻe i ka panana i kekahi ʻaoʻao o ka makeneka pā a hana hou i ka nānā ʻana. ʻO ka hopena o ka makeneka e huki ana i ka pou hema o ke kui panana ʻo ia ka pou ʻākau o ka makeneka, no ka mea, ua huki ʻia ka pou ʻākau o ke kui panana i ka pou hema o ka makeneka.
Nīnau 2: Kahua Magnetic a puni kahi uea e lawe ana i ke au pololei
Nīnau: Ke lawe nei kahi uea lōʻihi pololei i kahi au uila o 5 A. E hoʻoholo i ke kuhikuhi o ke kahua magnetic a puni ka uea ma kahi kiko 10 cm mai ka uea.
Kūkākūkā:
Hiki ke hoʻoholo ʻia ke kahua makeneka a puni kahi uea pololei e lawe ana i ke au me ka hoʻohana ʻana i ke kānāwai lima ʻākau. Eia ke ʻano:
1. E paʻa i ke kaula me kou lima ʻākau, me kou manamana nui e hōʻike ana i ke kuhikuhi o ke kahe ʻana o ke au (mai ka maikaʻi a i ka maikaʻi ʻole).
2. ʻO ke kuhikuhi o nā ʻūpā i kāʻei ʻia a puni ke kaula e hōʻike ana i ke kuhikuhi o ke kahua makeneka.
Eia kekahi laʻana, inā e kuhikuhi ʻia ke au i luna (e like me ka manamana nui), a laila ma kahi kiko he 10 cm mai ke kaula, e kaapuni ke kahua makeneka i ke kuhikuhi o ka neʻe ʻana o ka manamana lima ʻākau:
– Inā aia ke kiko i mua o ke kaula, kuhikuhi ke kahua makeneka i loko (i ka ʻāpana pepa/pale).
– Inā aia ke kiko ma hope o ke kaula, kuhikuhi ke kahua makeneka i waho (mai ka ʻāpana pepa/pale).
Nīnau 3: Ka Mana Lorentz ma nā ʻĀpana e Lawe Ana i ke Au
Nīnau: Ua komo kahi ʻāpana i hoʻopiʻi ʻia (+1.6 × 10^-19 C) e neʻe ana ma ka wikiwiki o 2 × 10^6 m/s i loko o kahi kahua magnetic o 0.01 T i kuhikuhi ʻia i waho mai ka ʻaoʻao. E hoʻoholo i ka nui a me ke kuhikuhi o ka ikaika Lorentz i ʻike ʻia e ka ʻāpana.
Kūkākūkā:
Hiki ke hōʻike ʻia ka ikaika Lorentz ma luna o kahi ʻāpana i hoʻopiʻi ʻia i loko o kahi kahua magnetic e ka hoohalike \( \vec{F} = q \vec{v} \times \vec{B} \).
– Ka uku ʻāpana, \(q\) = +1.6 × 10^-19 C
– Ka wikiwiki o ka ʻāpana, \( \vec{v} \) = 2 × 10^6 m/s (manaʻo ʻia e pili ana i ka axis-x)
– Ke kahua makeneka, \( \vec{B} \) = 0.01 T (ma waho o ka ʻaoʻao, e kū pono ana i ka axis-z)
No ke kuhikuhi o ka ikaika:
1. E hoʻohana hou i ke kānāwai lima ʻākau e hele i ka vector velocity (\( \vec{v} \)) a me ke kahua magnetic (\( \vec{B} \)).
2. Hahai nā manamana lima o ka lima ʻākau i ke kuhikuhi o ka wikiwiki (axis-x), pelu i nā manamana lima i waho o ka pepa (e like me ke kahua magnetic o ka axis-z), a laila hāʻawi ka manamana nui i ke kuhikuhi o ka ikaika Lorentz (axis-y).
Hiki ke helu ʻia ka nui o ka ikaika Lorentz \( F \) penei:
\[ F = q \cdot v \cdot B \cdot \sin \theta \]
ʻOiai ʻo \( \theta \) = 90° (ka wikiwiki e kū pono ana i ke kahua magnetic),
\[ F = (1.6 \times 10^{-19} C) \cdot (2 \times 10^6 m/s) \cdot (0.01 T) \sin (90°) \]
\[ F = 3.2 \times 10^{-21} N \]
ʻO ke kuhikuhi o ka ikaika e like me ka pelu ʻana o ka manamana lima (i ka ʻākau = axis-y maikaʻi).
Nīnau 4: Kahua Magnetic ma waenakonu o kahi Solenoid
Nīnau: Ua ʻike ʻia he 500 mau huli o kahi solenoid lōʻihi me ka lōʻihi o 0.5 m e lawe ana i ke au o 2 A. E helu i ka nui o ke kahua magnetic ma waenakonu o ka solenoid.
Kūkākūkā:
Hiki ke helu ʻia ke kahua magnetic i loko o kahi solenoid lōʻihi me ka hoʻohana ʻana i ke ʻano hana:
\[ B = \mu_0 n I \]
Ma hea:
– \( B \): ka nui o ke kahua makeneka i loko o ka solenoid (Tesla)
– \( \mu_0 \): ke koina permeability vacuum (\(4 \pi \times 10^{-7} \: T \cdot m/A\))
– \( n \): ka helu o nā huli no kēlā me kēia lōʻihi o ke anakahi (huli/mika), i hoʻohālikelike ʻia e like me \( n = \frac{N}{L} \)
– \( I \): ka nui o ke au e kahe ana ma o ka solenoid (Amperes)
No laila,
– \( N = 500 \)
– \( L = 0.5 m \)
– \( n = \frac{500}{0.5} = 1000 \: huli/m \)
– \( I = 2 A \)
Pēlā,
\[ B = \mu_0 \cdot n \cdot I \]
\[ B = (4 \pi \times 10^{-7} T \cdot m/A) \cdot (1000 \: huli/m) \cdot 2 A \]
\[ B = 8 \pi \times 10^{-4} T \]
\[ B \approx 2.51 \times 10^{-3} T \]
Nīnau 5: Hoʻokomo Uila
Nīnau: Aia kahi wili i 200 mau huli a ua kau ʻia i loko o kahi kahua magnetic e loli ana mai 0.1 T a i 0.5 T i loko o 0.25 s. E helu i ka voltage i hoʻokomo ʻia i hana ʻia i loko o ke wili.
Kūkākūkā:
Hiki ke helu ʻia ka induction electromagnetic me ka hoʻohana ʻana i ke kānāwai o Faraday:
\[ \mathcal{E} = -N \frac{\Delta \Phi_B}{\Delta t} \]
Ma hea,
– \( \mathcal{E} \): uila hoʻokomo ʻia (Volts)
– \( N \): helu o nā huli
– \( \Delta \Phi_B \): loli o ke kahe magnetic (Wb)
– \( \Delta t \): loli i ka manawa (mau)
Me \(\Delta \Phi_B = B \cdot A \); kahi ʻo A ka ʻāpana o ke koʻi. Eia naʻe, inā ʻaʻole e loli ka ʻāpana
\[ \mathcal{E} = -N \cdot \frac{\Delta B \cdot A}{\Delta t} \]
ʻOiai \(\Delta B = 0.5 T – 0.1 T = 0.4 T \),
Maka
\[ \mathcal{E} = -200 \cdot \frac{0.4 T \cdot A}{0.25 s} \]
\[ \mathcal{E} = -320 \cdot A \]
Inā ʻaʻohe wahi kikoʻī i hāʻawi ʻia (manaʻo ʻia he like),
ke hilinaʻi nei ka waiwai o ka induction ma ke ʻano linear ma luna o A.
Me ka manaʻolana, e kōkua kēia mau laʻana o nā pilikia magnetism iā ʻoe e hoʻomaopopo i nā manaʻo a me nā noi pono o ka magnetism. Hoʻohana mau ʻia kēia mau manaʻo a me nā loina ma nā pae hoʻonaʻauao like ʻole a ma nā noiʻi hohonu.
