Conduction, convection aur radiation
Short mein jawab
Garmi teen tareekon se chalti hai. Conduction mein garmi kan se kan tak jaati hai aur kan apni jagah rehte hain, zyaadatar thos mein. Convection mein garam liquid ya gas upar uthta hai aur thanda neeche aata hai, yaani kan khud chalte hain. Radiation mein garmi seedhe aati hai, bina medium ke, jaise Sooraj ki garmi.
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Garmi hamesha garam se thande ki taraf jaati hai
Jab do alag taapmaan ki cheezein ek doosre ko chhooti hain ya paas hoti hain, to garmi garam cheez se thandi cheez ki taraf jaati hai. Ye teen tareekon se chal sakti hai: conduction, convection aur radiation.
Conduction: garmi aage badhaana
Dhaatu ki ek patti ko stand se baandho, uspar mom se chaar pins chipkao, aur stand se door waale sire ko mombatti se garam karo. Lau ke sabse paas waali pin pehle girti hai, phir agli, aur aise hi. Garmi patti mein aage badhti hai, aur jaise-jaise kisi pin tak pahunchti hai, mom pighal jaata hai. Dhaatu ka har kan apne bagal ke kan ko garmi deta hai, par kan khud apni jagah se nahi hilte. Ye conduction hai, aur thos cheezon mein garmi chalne ka mukhya tareeka yahi hai.
Achhe aur kharaab conductor
Jo cheezein garmi ko aasaani se guzarne deti hain wo achhe conductor hain: taamba, aluminium, loha aur steel, yaani dhaatu. Jo nahi deti wo kharaab conductor yaani insulator hain: lakdi, plastic, kaanch, mitti, porcelain, oon aur hawa. Lakdi ya kaanch ki patti se pins nahi girengi, kyunki uspar garmi mushkil se chalti hai.
Hum roz dono tarah ki cheezein use karte hain. Bartan dhaatu ke bante hain taaki khaana jaldi garam ho, aur unke handle kharaab conductor ke. Mitti ya porcelain ke cup mein chai der tak garam rehti hai. Oon ke chhedon mein ya do patli razaaiyon ke beech band hawa shareer se garmi ko bahar jaane se rokti hai, isliye hum garam rehte hain. Bahut thandi ya bahut garam jagahon ke ghar bhi yahi tareeka apnaate hain, hollow bricks ya mitti bhari do lakdi ki parton waali deewaron se.
Convection: garam liquid ya gas upar uthta hai
Ek santulit dandi ke dono siron par kaagaz ke do cup ulte latkao aur ek ke neeche mombatti rakho. Wo cup upar uthta hai, kyunki uske andar ki hawa garam hokar phailti hai, halki hoti hai aur upar jaati hai. Dhoop mein rakha gubbaara isi wajah se phoolta hai, aur dhuaan, yaani garam gason aur chhote kanon ka mel, isliye uthta hai kyunki wo aas-paas ki hawa se garam hota hai.
Liquid bhi aise hi bartaav karte hain. Beaker ke tale mein potassium permanganate ka ek daana rakho aur neeche se garam karo: rangeen dhaara beech se upar uthti hai aur kinaaron se neeche aati hai. Garam paani upar jaata hai, thanda aur bhaari paani uski jagah lene neeche aata hai, aur ye chakkar tab tak chalta hai jab tak saara paani garam na ho jaaye. Liquid ya gas ke kanon ke asal mein chalne se garmi ka jaana convection hai.
Radiation: medium ki zaroorat nahi
Aag ke paas baithkar hum garmi mehsoos karte hain, jabki hamare aur lapton ke beech kuch nahi behta. Garmi seedhe radiation se aati hai, usi tarah jaise Sooraj ki garmi antariksh paar karke Dharti tak aati hai. Radiation ko koi medium nahi chahiye. Har cheez garmi radiate karti hai: lau se door rakha garam bartan isliye thanda hota hai kyunki wo apni garmi aas-paas radiate karta hai. Halke rang ke kapde apne upar padne waali zyaadatar garmi lauta dete hain aur gehre rang zyaada sokhte hain, isliye garmi mein halke aur sardi mein gehre rang pehente hain.
Teeno ki tulna
| Tareeka | Garmi kaise chalti hai |
|---|---|
| Conduction | kan se kan; kan apni jagah (thos) |
| Convection | kan chalte hain; garam upar (liquid, gas) |
| Radiation | garam cheez se seedhe; medium nahi chahiye |
Teeno ek saath bhi ho sakte hain. Bartan mein paani garam karte samay bartan conduction se, paani convection se garam hota hai, aur haathon ko garmi radiation se lagti hai. Samudra ke kinaare convection hawa ki disha kaise badalta hai, ye padho land breeze aur sea breeze mein. Textbook ke sawaalon ke jawab Chapter 7 ke NCERT solutions mein hain; poore chapter ke liye Chapter 7 ke notes.
Practice karo
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Kaunsa material garmi ka achha conductor hai?
Jawab dekho
Jawab: (b) Taamba
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Jalti lakdi ka dhuaan upar kis wajah se uthta hai?
Jawab dekho
Jawab: (b) convection
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Aag ke paas baithne par garmi hum tak mukhya roop se kaise aati hai?
Jawab dekho
Jawab: (c) radiation
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Sardi mein ek moti razaai ki jagah do patli razaaiyan kyun behtar hain?
Jawab dekho
Jawab: Do patli razaaiyon ke beech band hawa ki parat garmi ki kharaab conductor hai, isliye shareer se garmi kam bahar jaati hai aur hum zyaada garam rehte hain.
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Chulhe par bartan mein paani garam karte samay garmi bartan, paani aur hamare haathon tak kaise pahunchti hai?
Jawab dekho
Jawab: Bartan ko lau se garmi conduction se milti hai, andar ka paani convection se garam hota hai, aur lau aur garam bartan ke paas jo garmi mehsoos hoti hai wo radiation se aati hai.
Students ke sawal
Conduction, convection aur radiation mein kya farq hai?
Conduction mein garmi kan se kan tak jaati hai, kan apni jagah nahi chhodte. Convection mein liquid ya gas ke kan khud chalte hain aur garmi saath le jaate hain. Radiation ko kanon ki zaroorat hi nahi: garmi garam cheez se seedhe aati hai, khaali jagah se bhi.
Khaana pakaane ke bartan dhaatu ke kyun hote hain?
Dhaatu garmi ke achhe conductor hain, isliye lau ki garmi jaldi bartan se khaane tak pahunchti hai. Unke handle aksar plastic ya lakdi jaise kharaab conductor ke hote hain, taaki pakadne mein thande rahein.
Hawa garmi ki achhi conductor hai ya kharaab?
Kharaab. Isiliye oon ke kapdon mein, do patli razaaiyon ke beech ya hollow bricks ke andar band hawa sardi mein hamein aur hamare gharon ko garam rakhti hai.
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