Class 7 Science Chapter 7 NCERT Solutions Hinglish mein: Heat Transfer in Nature

Curiosity (Reprint 2026-27) ke Chapter 7, Heat Transfer in Nature, ki Activities 7.1 se 7.5, text ke sawaal, saare 10 “Let Us Enhance Our Learning” sawaal aur exploratory projects ke jawab. Page numbers book se match karte hain. Activities mein sample readings hain; tumhari alag hongi. Short notes: Chapter 7 notes.

Conduction (pages 89–92)

Activity 7.1: garam dhaatu ki patti par pins.

Table 7.1	Sample jawab
Andaaza	Lau ke sabse paas waali pin I pehle giregi
Dekha	Pins ek-ek karke giri: I, II, III, phir IV
Kaaran	Garmi garam sire se patti mein chalti hai; lau ke paas ka mom pehle pighalta hai

Saari pins ek saath kyun nahi girti? Garmi ko patti mein chalne mein samay lagta hai, isliye wo pehle pin I tak aur sabse baad mein pin IV tak pahunchti hai. Kan se kan garmi ka jaana conduction hai.

Lakdi ya kaanch ki patti ho to? Pins nahi girengi, kyunki lakdi aur kaanch garmi ke kharaab conductor hain: unme garmi mushkil se chalti hai.

Table 7.2 (sample):

Material	Achha ya kharaab conductor
Steel, taamba, aluminium, loha	achha conductor
Lakdi, plastic, kaanch, rubber	kharaab conductor
Mitti, porcelain, kapda, oon	kharaab conductor
Hawa	kharaab conductor

Kya tumhari list mein hawa hai? Hawa kharaab conductors mein aati hai. Isiliye oon ke kapdon mein ya do patli razaaiyon ke beech band hawa hamein garam rakhti hai.

Kya aise ghar ban sakte hain jin par bahar ki garmi-sardi ka kam asar ho? Haan: mitti aur gobar bhari do lakdi ki parton waali deewarein, jaise Uttarkashi ke Mori block mein, ya hollow bricks ki baahari deewarein. Lakdi, mitti aur band hawa kharaab conductor hain, isliye andar-bahar garmi ka aana-jaana dheema hota hai.

Convection (pages 92–94)

Activity 7.2 (Table 7.3): mombatti ke upar waala cup upar uthta hai. Us cup ki hawa garam hokar phailti hai, zyaada jagah leti hai aur halki hoti hai, isliye upar uthkar cup ko utha deti hai.

Dhuaan upar kyun ja raha hai? Dhuaan garam gason aur chhote thos kanon ka mel hai. Wo aas-paas ki hawa se garam aur halka hota hai, isliye upar uthta hai.

Activity 7.3: kya garam hone par liquid bhi uthte hain? Haan. Potassium permanganate ki rangeen dhaara beech se upar uthti hai aur kinaaron se neeche aati hai. Tale ka paani garam hokar phailta hai, halka hokar uthta hai; kinaaron ka thanda paani uski jagah neeche aata hai, jab tak saara paani garam na ho jaaye. Ye convection hai.

Land aur sea breeze (pages 94–96)

Activity 7.4 (Table 7.4, sample readings):

Samay	Mitti aur paani
0 minute	mitti 28 °C, paani 28 °C
5 minute	mitti 31 °C, paani 29 °C
10 minute	mitti 34 °C, paani 30 °C
15 minute	mitti 36 °C, paani 31 °C
20 minute	mitti 38 °C, paani 32 °C

Taapmaan baraabar nahi badha. Mitti jaldi garam hui: 20 minute mein lagbhag 10 °C, paani lagbhag 4 °C. Andar laane par mitti jaldi thandi bhi hui. Isliye din mein zameen garam hoti hai aur sea breeze samudra se zameen ki taraf chalti hai; raat mein zameen thandi hoti hai aur land breeze zameen se samudra ki taraf chalti hai.

Radiation (pages 96–97)

Aag ki garmi hum tak kaise aati hai? Seedhe, radiation se, jise medium ki zaroorat nahi. Sooraj ki garmi bhi Dharti tak aise hi aati hai.

Lau se door rakha garam bartan thanda kyun hota hai? Wo apni garmi aas-paas radiate karta hai.

Dive Deeper: garmi mein halke, sardi mein gehre kapde. Halke rang ke kapde apne upar padne waali zyaadatar garmi lauta dete hain, isliye garmi mein thanda rakhte hain. Gehre rang zyaada garmi sokhte hain, isliye sardi mein garam rakhte hain.

Bartan mein paani (Fig. 7.8) aur bukhari: bartan conduction se, paani convection se garam hota hai, aur lau aur bartan ke paas ki garmi radiation hai. Bukhari teeno se khaana pakaati aur kamra garam karti hai.

Water cycle aur risna (pages 98–101)

Activity 7.5 (Table 7.5):

Botal	Andaaza aur dekha
Clay	bahut dheere
Ret	dheere
Gravel	tez

Kya nateeje andaaze se mile? Aam taur par haan: paani gravel se sabse tez aur clay se sabse dheere risata hai, kyunki gravel ke tukdon ke beech zyaada jagah hoti hai. Paani zameen ki satah se kaise risata hai? Mitti aur chattaanon ke kanon ke beech ki jagah se; ye infiltration hai, aur jama paani aquifers mein groundwater hai.

Let Us Enhance Our Learning (pages 102–104)

1. Sahi option chuno

(i) (c) A achha conductor hai aur B kharaab conductor. A dhaatu ka bartan hai, jo khaana garam karta hai; B handle hai, jo pakadne ke liye thanda rehna chahiye.

(ii) (d) Pins II aur III lagbhag ek saath giregi. Mombatti patti ke beech mein, II aur III ke neeche hai, isliye garmi pehle aur saath-saath unhi tak pahunchti hai, aur I aur IV tak baad mein.

(iii) (c) Chhat par. Dhuaan garam hota hai aur convection se upar uthta hai, isliye pehle chhat tak pahunchta hai.

2. Tapakte gilaas ko doosre gilaas mein rakhna

Haan. Dono gilaason ke beech hawa ki parat band ho jaati hai, aur hawa garmi ki kharaab conductor hai. Ye bahar ki garmi ko lassi tak dheere pahunchne deti hai, isliye lassi der tak thandi rehti hai. (Baahari gilaas tapakna bhi rok leta hai.)

3. Sahi ya galat

(i) Galat. Thos mein garmi zyaadatar conduction se chalti hai; kan idhar-udhar nahi ja sakte. (ii) Sahi. Convection mein liquid ya gas ke kan chalte hain aur garmi saath le jaate hain. (iii) Galat. Clay ke kanon ke beech bahut chhoti jagah hoti hai, isliye ret se kam paani risata hai. (iv) Sahi. Raat mein zameen se samudra ki taraf thandi hawa chalti hai; ye land breeze hai.

4. Pighalti barf ko garmi kahan se milti hai?

Aas-paas ki garam cheezon se: chaaron taraf ki hawa aur wo bartan jisme barf rakhi hai. Garmi in garam cheezon se thandi barf tak jaati hai: chhoone par conduction se, garam hawa ke chalne se (convection), aur paas ki cheezon se radiation se.

5. Neeche ki taraf mudi agarbatti ka dhuaan

Dhuaan phir bhi upar jaata hai. Dhuaan garam gason aur chhote kanon ka mel hai, jo aas-paas ki hawa se garam aur halka hai, isliye jalte sire se uthkar agarbatti ke bagal se upar jaata hai.

6. Kaunsa thermometer zyaada dikhayega?

Fig. 7.16(a) waala. Wahan lau test tube ke tale ko garam karti hai, isliye garam paani uthta hai aur thanda neeche aata hai, aur convection jaldi thermometer ke aas-paas ka saara paani garam kar deta hai. Fig. 7.16(b) mein lau tube ko upar ke paas garam karti hai jabki thermometer ka bulb tale mein hai. Garam paani upar hi rehta hai, aur paani kharaab conductor hai, isliye bulb ke aas-paas ka paani thanda rehta hai.

7. Garam ilaakon mein hollow bricks

Hollow bricks ke andar band hawa garmi ki kharaab conductor hai. Ye bahar ki garmi ko ghar ke andar dheere aane deti hai, isliye garmi mein kamre thande rehte hain (aur sardi mein garmi andar rehti hai).

8. Bade jal srot bahut zyaada taapmaan kaise rokte hain

Paani zameen se dheere garam aur dheere thanda hota hai. Din mein jal srot zameen se thanda rehta hai, aur thandi sea breeze paas ka taapmaan kam karti hai. Raat mein paani zameen se garam rehta hai, isliye paas ki hawa bahut thandi nahi hoti. Isliye bade jal sroton ke paas na din bahut garam hote hain, na raatein bahut thandi.

9. Paani zameen mein kaise risata aur jama hota hai

Satah ka baarish ka paani mitti aur chattaanon ke kanon ke beech ki jagah se neeche risata hai; ye infiltration hai. Jahan jagah chaudi, khuli aur judi ho, jaise gravel aur ret mein, wahan ye tez hota hai, aur clay mein dheere. Paani mitti ke beech ki jagah aur chattaanon ki daraaron mein groundwater bankar jama hota hai, aur use rakhne waali parat aquifer hai, jisse kuen aur borewell paani nikaalte hain.

10. Water cycle paani ko baant-ta aur bharta hai

Sooraj samudron, nadiyon aur jheelon ka paani bhaap banata hai, aur paudhe bhaap chhodte hain. Hawa bhaap ko le jaati hai, wo thandi hokar baadal banti hai, aur precipitation use baarish, barf aur ole ke roop mein neeche laata hai, aksar wahan se door jahan se wo uthi thi: zameen par, pahaadon par aur samudra par. Baarish taalaab, nadiyan aur jheelein bharti hai aur zameen mein risakar aquifers bharti hai; sardi ki barf garmi mein pighal kar nadiyon ko paani deti hai. Is tarah paani samudron se zameen aur wapas chalta rehta hai, har srot ko bharta hai, aur Dharti par paani ki kul maatra ek jaisi rehti hai.

Exploratory projects (page 104)

• Rainwater harvesting site ya recharge pit dekhna (report ke sample points): baarish kahan jama hoti hai, jaise chhat par; pipe se kaise laayi jaati hai; kaise saaf hoti hai, jaise gravel aur ret ki parton se (Extra); aur tank mein rakhi jaati hai ya gaddhe mein zameen ke andar risne di jaati hai. Label waale chitra aur wahan ke logon ki baatein jodo.
• Dhaatu ki chhad par lipta kaagaz: kaagaz aasaani se nahi jalta. Dhaatu, ek achha conductor, mombatti ki garmi kaagaz se door le jaata hai, aur chhad ghumaane se garmi aur phailti hai, isliye kaagaz jalne laayak garam nahi hota.
• Mombatti ke upar kaagaz ka spiral: spiral ghoomne lagta hai. Mombatti se garam hui hawa upar uthti hai (convection) aur upar jaate hue tirchhe kaagaz ko dhakelti hai.

Aur padho conduction, convection aur radiation, land breeze aur sea breeze aur water cycle aur groundwater mein.