Electric current

Elektr maydoni
Elektr maydoni tushunchasi Maykl Faraday tomonidan kiritilgan. Elektr maydoni uni o'rab turgan bo'shliqda zaryadlangan jism tomonidan yaratiladi va bu maydon ichida joylashgan har qanday boshqa zaryadlarga ta'sir qiluvchi kuchga olib keladi. Elektr maydoni ikki zaryad o'rtasida tortishish maydonining ikkita massa o'rtasida ta'siriga o'xshash tarzda harakat qiladi va u kabi cheksizlik tomon cho'ziladi va masofa bilan teskari kvadrat munosabatni ko'rsatadi. Biroq, muhim farq bor. Gravitatsiya har doim ikki massani bir-biriga tortadigan tortishish bilan ishlaydi, elektr maydoni esa tortishish yoki itarilishga olib kelishi mumkin. Sayyoralar kabi katta jismlar odatda aniq zaryadga ega emasligi sababli, masofadagi elektr maydoni odatda nolga teng. Shunday qilib, tortishish kuchi ancha zaifroq bo'lishiga qaramay, koinotdagi masofadagi hukmron kuchdir.
Tekis o'tkazgich ustidagi musbat zaryaddan chiqadigan maydon chiziqlari
Elektr maydoni odatda fazoda o'zgarib turadi va uning har qanday nuqtadagi kuchi, agar bu nuqtaga joylashtirilsa, statsionar, ahamiyatsiz zaryad tomonidan seziladigan kuch (zaryad birligi uchun) sifatida aniqlanadi. "Sinov zaryadi" deb ataladigan kontseptual zaryad o'z elektr maydonining asosiy maydonni bezovta qilmasligi uchun juda kichik bo'lishi kerak va magnit maydonlarning ta'sirini oldini olish uchun ham harakatsiz bo'lishi kerak. Elektr maydoni kuch nuqtai nazaridan aniqlanganidek va kuch ham kattalikka, ham yo'nalishga ega bo'lgan vektor bo'lib, elektr maydoni vektor maydonidir.

The study of electric fields created by stationary charges is called electrostatics. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term 'lines of force' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves.

A hollow conducting body carries all its charge on its outer surface. The field is therefore zero at all places inside the body.  This is the operating principal of the Faraday cage, a conducting metal shell which isolates its interior from outside electrical effects.The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between the charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre.

Statsionar zaryadlar tomonidan yaratilgan elektr maydonlarini o'rganishga elektrostatika deyiladi. Maydonni har qanday nuqtada yo'nalishi maydon bilan bir xil bo'lgan xayoliy chiziqlar to'plami bilan tasvirlash mumkin. Ushbu kontseptsiya Faraday tomonidan kiritilgan bo'lib, uning "kuch chizig'i" atamasi hali ham ba'zida qo'llaniladi. Maydon chiziqlari - bu nuqta musbat zaryad maydon ichida harakat qilishga majbur bo'lganida amalga oshirishga intiladigan yo'llar; ammo ular hech qanday jismoniy mavjud bo'lmagan xayoliy tushunchadir va maydon chiziqlar orasidagi barcha bo'shliqqa kirib boradi. Statsionar zaryadlardan chiqadigan maydon chiziqlari bir nechta asosiy xususiyatlarga ega: birinchidan, ular musbat zaryadlardan kelib chiqadi va manfiy zaryadlarda tugaydi; ikkinchidan, ular har qanday yaxshi o'tkazgichga to'g'ri burchak ostida kirishlari kerak, uchinchidan, ular hech qachon o'zlarini kesib o'tmasliklari va yaqinlashmasliklari uchun.

Bo'shliq o'tkazuvchi jism o'zining barcha zaryadini tashqi yuzasida olib yuradi. Shunday qilib, maydon tananing barcha joylarida nolga teng. Bu Faraday qafasining ishlash printsipi bo'lib, uning ichki qismini tashqi elektr ta'siridan ajratib turadigan o'tkazuvchi metall qobiqdir. Elektrostatika tamoyillari yuqori voltli uskunalarni loyihalashda muhim ahamiyatga ega. Har qanday muhit bardosh bera oladigan elektr maydon kuchining cheklangan chegarasi mavjud. Bu nuqtadan tashqari, elektr uzilishi sodir bo'ladi va elektr yoyi zaryadlangan qismlar o'rtasida chaqnashga olib keladi. Masalan, havo har santimetrda 30 kV dan ortiq elektr maydon kuchlarida kichik bo'shliqlar bo'ylab yoyga moyil bo'ladi.

Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre. The most visible natural occurrence of this is lightning, caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh.

The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor, the sharp spike of which acts to encourage the lightning stroke to develop there, rather than to the building it serves to protect.

Field lines emanating from a positive charge above a plane conductor

Kattaroq bo'shliqlarda uning parchalanish kuchi zaifroq, ehtimol santimetr uchun 1 kV. Buning eng ko'zga ko'ringan tabiiy hodisasi chaqmoq bo'lib, zaryad bulutlarda ko'tarilgan havo ustunlari orqali ajralib chiqadi va havodagi elektr maydonini bardosh bera oladigan darajadan kattaroqqa ko'taradi. Katta chaqmoq bulutining kuchlanishi 100 MV gacha bo'lishi mumkin va zaryadsizlanish energiyasi 250 kVt / soatgacha bo'lishi mumkin.

Maydon kuchiga yaqin atrofdagi o'tkazuvchi jismlar katta ta'sir ko'rsatadi va u o'tkir uchli jismlar atrofida egilishga majbur bo'lganda, ayniqsa kuchli bo'ladi. Ushbu printsip chaqmoq o'tkazgichida qo'llaniladi, uning o'tkir boshi u erda himoya qilish uchun xizmat qiladigan binoni emas, balki u erda chaqmoq urishini rivojlanishiga yordam beradi.

Tekis o'tkazgich ustidagi musbat zaryaddan chiqadigan maydon chiziqlari