Ka wehewehe ʻana o ke kānāwai o Ohm
Ma aneane nā alakaʻi metala āpau, ua kūlike ke kahua uila me ka nui o ke au uila, kahi e mau ai ka lakio o ke kahua uila i ka nui o ke au uila. Hōʻike ʻia ma ka makemakika ma o ka hoohalike:
ρ = E / J
E = kahua uila , ρ = resistivity , J = density au
Ua kapa ʻia ke ʻano mau o ρ he resistivity, nona ka waiwai mau a ʻaʻole ia e hilinaʻi i ke kahua uila e hāʻawi ai i ke au uila.
Inā piʻi ke kahua uila, piʻi pū ka nui o ke au uila, ʻoiai inā emi ke kahua uila, e emi pū ka nui o ke au uila.
i paʻa ai ka lakio o ke kahua uila i ka nui o ke au uila. ʻO kēia ka ʻōlelo kānāwai a Ohm. No laila, wehewehe ka hoohalike ma luna i ke kānāwai o Ohm ke paʻa wale ʻo ρ a ʻaʻole hilinaʻi i ke kahua uila. ʻAʻole pili ke kānāwai o Ohm inā loli ka waiwai o ρ i ka wā e loli ai ke kahua uila.
Eia nō naʻe, ʻoi aku ka maʻalahi o ke ana ʻana i ka hiki uila (V) ma mua o ke kahua uila (E), no laila ʻoi aku ka maʻalahi o ke ana ʻana i ke au uila (I) ma mua o ka nui o ke au uila (J). No laila, me ka ʻōlelo ʻia ma ke kahua uila, ka nui o ke au uila a me ka resistivity (ρ), ua hōʻike ʻia ke kānāwai o Ohm ma ka hiki uila, ke au uila a me ke kū'ē uila (R).
E nānā mua i kahi alakaʻi uea nona ka lōʻihi (l), ka ʻāpana ʻāpana (A) a aia kahi ʻokoʻa hiki ke uila (V) ma waena o nā wēlau ʻelua o ke uea. Inā like ke kahua uila homogeneous, a laila ua hōʻike ʻia ka pilina ma waena o ke kahua uila a me ka ʻokoʻa hiki ke uila ma ka hoohalike V = E s (ua kūkākūkā ʻia kēia hoohalike ma ka hiki ke uila). Inā like ka nui o nā au uila homogeneous,
a laila ua hōʻike ʻia ka pilina ma waena o ke au uila a me ka nui o ke au uila ma ka hoohalike I = JA (ua kūkākūkā ʻia kēia hoohalike ma ke kumuhana o ke au uila).
No ka loaʻa ʻana o kahi kaulike e hōʻike ana i ka pilina ma waena o ka hiki ke uila (V), ke au uila (I) a me ke kū'ē uila (R),
e pani iā E a me J ma ke kaulike o ka resistivity, me E ma ke kaulike o ka hiki ke uila a me J ma ke kaulike o ke au uila:
He hoohalike kēia e wehewehe ana i ka pilina ma waena o ka hiki uila (V), ke au uila (I) a me ke kū'ē uila (R) i loko o kahi alakaʻi. Ma muli o kēia hoohalike, hiki ke ʻōlelo ʻia ʻo ke kū'ē uila i loko o kahi alakaʻi he hoʻohālikelike ia o ka ʻokoʻa hiki uila i ke au uila i loko o ke alakaʻi.
ʻŌlelo ke kānāwai o Ohm he paʻa ka lakio ma waena o ka ʻokoʻa hiki ke uila i ke au uila. I nā huaʻōlelo ʻē aʻe, wehewehe kēia kaulike i ke kānāwai o Ohm ke paʻa wale ke kū'ē uila (R). ʻAʻole pili ke kānāwai o Ohm inā ʻaʻole paʻa ke kū'ē uila.
Ma ke kaulike ma luna, ʻo ke kū'ē uila (R) i loko o kahi alakaʻi he pilina pū kekahi me ka resistivity (ρ), ka lōʻihi o ke alakaʻi (l) a me ka ʻāpana ʻāpana (A) o ke alakaʻi. Ua hōʻike ʻia ma ka makemakika ma ke kaulike:
ʻO ke kaulike o ke kānāwai o Ohm
Ua wehewehe ʻia ke kānāwai o Ohm e ʻelua mau kaulike, ʻo ia hoʻi ʻo ρ = E/J a me R = V/I. Pono e hoʻomanaʻo ʻia ʻo kēia mau kaulike ʻelua he mau kaulike o ke kānāwai o Ohm wale nō ke kūpaʻa ʻo ρ a kūpaʻa ʻo R. Inā loli ʻo ρ a me R o kahi alakaʻi, ʻaʻole wehewehe kēia mau kaulike ʻelua i ke kānāwai o Ohm, akā wehewehe ʻo ρ = E/J i ke kūʻē ʻana o kahi ʻano alakaʻi a wehewehe ʻo R = V/I i ke kūʻē uila o kahi alakaʻi.
Hiki ke kākau ʻia ke kaulike ρ = E/J penei E = ρ J. Ke paʻa ʻo ρ, kūlike ʻo E me J, ʻo ia hoʻi inā piʻi ʻo E a laila piʻi ʻo J a inā emi ʻo E a laila emi ʻo J.
Pēlā nō, hiki ke kākau ʻia ke kaulike R = V/I ma ke ʻano he V = I R. Ke paʻa ʻo R a laila kūlike pololei ʻo V me I, ʻo ia hoʻi inā piʻi ʻo V, a laila piʻi ʻo I a inā emi ʻo V, a laila emi ʻo I.
ʻO ka mea e mālama ana i ke kānāwai o Ohm ua ʻōlelo ʻia he ohmic, ʻoiai ʻo ka mea i mālama ʻole i ke kānāwai o Ohm ua ʻōlelo ʻia he nonohmic. ʻO ka hapa nui o nā alakaʻi metala he ohmic, ʻoiai he nui nā mea ʻē aʻe he nonohmic.
Ma nā mea nonohmic, ʻaʻole mau ke kū'ē uila a hilinaʻi ʻia i ke au uila a me ka ʻokoʻa hiki uila. ʻO ke ʻano kēia inā loli ke au uila a laila loli pū ke kū'ē uila o ka mea, a inā loli ke volta uila a laila loli pū ke kū'ē uila o ka mea. Ma muli o ka loli o ke kū'ē uila ma mua o ka mea nonohmic, ʻaʻole kūlike pololei ke volta uila (V) i ke au uila (I).
Kiʻi V, I a me R
I loko o ka mea ohmic, ʻo ka lakio V a i I he paʻa, kahi i hōʻike ʻia e kahi laina pololei. ʻO kahi laʻana o ka mea ohmic he alakaʻi metala. I kēia manawa, i loko o ka mea nonohmic, ʻaʻole paʻa ka lakio o V a i I, kahi i hōʻike ʻia e kahi laina piʻo. ʻO nā laʻana o nā mea nonohmic he mau diode semiconductor a me nā transistors.
Pili wale ke kānāwai ohm i nā mea ohmic a ʻaʻole pili i nā mea āpau, no laila ʻaʻole kūpono ke ʻōlelo ʻana i nā kānāwai e like me ke kānāwai o Newton a i ʻole nā kānāwai kino ʻē aʻe. Pili maoli ke kānāwai kino i nā mea āpau, ʻaʻole wale i kekahi mau mea. Akā ua lilo ka ʻōlelo ʻana i ke kānāwai ohm i mea maʻamau, no laila ua kapa ʻia ʻo ia ke kānāwai ohm, inā e hoʻomanaʻo ʻia ʻo ke kānāwai ohm e pili wale i nā mea ohmic.
