NCERT Solutions Class 7 Science Chapter 3: Electricity: Circuits and their Components (Hinglish)

Curiosity, Class 7 Science ki kitaab (Reprint 2026-27) ke Chapter 3, Electricity: Circuits and their Components, ke har sawaal ke jawab: shuruaat ke sawaal, Activities 3.1 se 3.11, Table 3.1 aur 3.3 ke saath, Dive Deeper boxes, Let Us Enhance Our Learning ke saare gyaarah sawaal aur Exploratory Projects. Page numbers kitaab ke hisaab se hain (pages 23–40). Activities ke jawab wo nateeje dete hain jinki ummeed hai; apne observations khud likho. Chhote notes: Chapter 3 ke notes.

Bijli ke upyog (pages 23–24)

Nihal ki lists mein aur upyog jodo. Khaana banaana: induction cooktop, rice cooker, sandwich maker. Roshni: aspataal, stadium, railway station, traffic signal. Yaatayaat: metro train, e-rickshaw aur electric car. Garam aur thanda karna: cooler, hair dryer, bijli ki press. Manoranjan: music system, cinema projector, video games. Sanchaar: Wi-Fi router, landline phone, laptop. Anya: washing machine, silaai machine, vacuum cleaner.

Upyogon ko baantne ke aur tareeke. Jagah ke hisaab se (ghar, school, aspataal, khet, factory); bijli kis cheez mein badalti hai (roshni, garmi, thandak, gati, aawaaz); srot ke hisaab se (deewaar ka socket ya battery); ya device ko kitni bijli chahiye (remote jaise chhote, AC jaise bade).

Activity 3.1: Torch (page 24)

Kya lamp jalta hai, aur andar kya hai? Switch ki ek position mein lamp jalta hai aur doosri mein nahi. Andar do ya zyaada electric cells hote hain.

Torch ka lamp switch ki ek hi position mein kyun jalta hai? Us position mein switch ek gap ko band kar deta hai, jisse cells se lamp tak aur waapas circuit poora hota hai aur current behta hai. Doosri position mein gap current ko rok deta hai.

Activity 3.2: Electric cell (page 25)

Cell ke jis sire pe chhoti ubhri dhaatu ki topi hai uspe + likha hai, ye positive terminal hai; jis sire pe chapti dhaatu ki plate hai uspe − likha hai, ye negative terminal hai.

Activity 3.3: Torch mein cells (page 25)

Kya cells kisi khaas kram mein rakhe jaate hain? Haan. Lamp tabhi jalta hai jab ek cell ka positive terminal agle ke negative terminal ko chhoota hai. Ek cell ulta ho to lamp nahi jalta. Aise jude cells battery banaate hain.

Activity 3.4: Incandescent lamp (page 26)

Kya dikhta hai, aur kaunsa hissa chamakta hai? Kaanch ke bulb ke beech laga ek patla taar, filament, chamakta hai. Filament kaise laga hai? Wo do mote taaron ke beech tika hai. Ek mota taar base ke dhaatu ke case se aur doosra base ke beech ki dhaatu ki nok se juda hai. Ye lamp ke do terminal hain, aur ek doosre ko chhoote nahi.

Activity 3.5: LED (page 27)

LED ke andar filament nahi hota, aur uske do taaron mein se ek doosre se lamba hai. Lamba taar positive aur chhota taar negative terminal hai.

Activity 3.6: Lamp jalaana (pages 27–30)

Table 3.1, andaaze aur observations. Andaaze alag ho sakte hain; observations ye hain:

• 1: lamp jalta hai; lamp ka har terminal cell ke alag terminal se juda hai.
• 2: nahi jalta; negative taraf ke taar mein gap hai.
• 3: nahi jalta; positive taraf ke taar mein gap hai.
• 4: nahi jalta; lamp ke dono taar positive terminal pe jaate hain aur negative terminal khula chhoota hai.
• 5: nahi jalta; lamp ke dono taar negative terminal pe jaate hain aur positive terminal khula chhoota hai.
• 6: lamp jalta hai; taar ek doosre ko kaatte hain, par lamp ka har terminal phir bhi cell ke alag terminal tak pahunchta hai.

Kya farq ki wajah dhoondh sakte ho? Lamp tabhi jalta hai jab cell ke ek terminal se, lamp se hokar, doosre terminal tak poora raasta ho. 2 aur 3 mein raasta toota hai; 4 aur 5 mein current ke paas lamp se hokar + se − tak jaane ka raasta nahi.

Activity 3.7: LED jalaana (pages 30–31)

Holder waali battery ka positive terminal kaunsa hai? Holder ka jo terminal ek cell ke positive terminal (dhaatu ki topi) se juda hai wo positive hai; jo doosre cell ke negative terminal se juda hai wo negative.

Kya LED jalta hai? Battery ka positive taar LED ke lambe taar pe ho to haan. Taar badal do to nahi, kyunki LED mein current sirf ek disha mein guzarta hai.

Dive Deeper: agal-bagal rakhe cells. Dibbe mein ek mota taar ya dhaatu ki patti ek cell ke positive terminal ko agle ke negative terminal se jodti hai, aur andar bane + aur − nishaan batate hain ki har cell kaise rakhna hai.

Activities 3.8 aur 3.9: Switch (page 32)

Switch torch ko on ya off kaise karta hai? Ghar pe bane switch ki OFF position (Fig. 3.12a) mein lamp nahi jalta; gap hai, isliye circuit khula hai. Jab safety pin ghumaakar doosri drawing pin ko chhuaate hain (Fig. 3.12b), gap band hota hai, circuit closed hota hai, current behta hai aur lamp jalta hai.

Activity 3.10: Circuit diagrams (pages 33–34)

Kya circuits ko aur saral tarah dikha sakte hain? Haan, symbols se. Fig. 3.12a ke liye: ek loop mein cell, lamp aur OFF position ka switch. Fig. 3.10c ke liye: do cells ki battery aur LED, jiska triangle us disha mein ho jidhar current behta hai, yaani battery ki lambi line se nikalkar. Ye Fig. 3.14a aur 3.14b jaise hi hain.

Electrical conductors and insulators (page 34)

Dhaatu ke taar kyun, aur plastic ya rubber ka cover kyun? Dhaatuon mein current aasaani se behta hai, isliye ve achhe taar bante hain. Plastic aur rubber current nahi guzarne dete, isliye inka cover current ko taar mein rakhta hai aur hamein jhatke se bachaata hai.

Activity 3.11: Conductors aur insulators (pages 35–36)

Table 3.3, poori. Lamp jalta hai (Haan/Nahi) aur nishkarsh:

• Chhadi (lakdi): Nahi, insulator.
• Scale (plastic): Nahi, insulator.
• Choodi (kaanch): Nahi, insulator.
• Kaagaz ki patti (kaagaz): Nahi, insulator.
• Mombatti (mom): Nahi, insulator.
• Chaabi (dhaatu): Haan, conductor.
• Eraser (rubber): Nahi, insulator.
• Apni panktiyan, jaise sikka (dhaatu): Haan, conductor; aluminium foil (dhaatu): Haan, conductor; cork: Nahi, insulator.

Kya har padaarth se lamp jala? Nahi, sirf dhaatu ki cheezon se. Extra: pencil ki lead (graphite) bhi current chalaati hai, haalaanki ek cell se lamp shaayad halka hi jale.

Let Us Enhance Our Learning (pages 37–39)

1. Galat kathan chuno. (i) Switch circuit mein current ka srot hai. Srot cell ya battery hai; switch sirf circuit ko poora karta ya todta hai.

2. A aur B ke beech kaunsa padaarth lagaane se lamp nahi jalega? Koi bhi insulator, jaise plastic ka scale, rubber ka eraser, lakdi ki chhadi, kaanch ki choodi, kaagaz ki patti ya mombatti. Chaabi ya sikke jaisi dhaatu ki cheez se lamp jalta hai.

3. Fig. 3.17 mein ek lamp ka filament toot jaaye, to kya doosra jalega? Nahi. Dono lamp aur battery ek hi loop mein hain, isliye toota filament us akele raaste mein gap chhod deta hai. Current nahi behta, aur doosra lamp bhi bujh jaata hai.

4. Taaron ke siron se insulation nahi hataaya gaya. Kya lamp jalega? Nahi. Plastic ka cover insulator hai, isliye taaron ki dhaatu terminals ko nahi chhooti, raasta poora nahi hota aur current nahi behta.

5. Saral torch ka circuit diagram banao. Do cells ki battery, ek switch aur ek lamp, sab ek loop mein.

6. Fig. 3.18 mein (L1, S2, L2, battery aur S1 sab ek loop mein hain):

• (i) S2 ON, S1 OFF: koi lamp nahi jalta.
• (ii) S2 OFF, S1 ON: koi lamp nahi jalta.
• (iii) S1 aur S2 dono ON: L1 aur L2 dono jalte hain.
• (iv) S1 aur S2 dono OFF: koi lamp nahi jalta.

Raasta ek hi hai, isliye kahin bhi khula switch dono lampon ka current rok deta hai.

7. Vidyut ka lamp kyun nahi jala, aur kaise pata karein? Sambhaavit wajahein: cell khatm ho chuka hai; lamp fuse ho gaya hai (toota filament) ya holder mein dheela hai; koi jod ya holder ka screw dheela hai; kisi taar ke sire se plastic nahi hataaya gaya; koi taar apne cover ke andar toota hai; safety pin doosri drawing pin ko theek se nahi chhoo rahi; ya cell holder ke contacts ko nahi chhoo raha. Pata karne ke liye ek-ek hissa jaancho: cell ko theek lamp ke saath aazmaao, lamp ko achhe cell ke saath aazmaao, har jod kaso, har taar conduction tester se jaancho, aur switch ke dono taar milaakar dekho ki gadbad switch mein to nahi.

8. Fig. 3.20 ke kin circuits mein lamp ya LED nahi jalega? Sirf (c) mein. (a) aur (b) mein lamp jalte hain, kyunki incandescent lamp cell ki kisi bhi disha mein kaam karta hai. (c) mein battery ki lambi line, yaani positive terminal, daayein hai, isliye current LED tak uske triangle ki ulti disha mein pahunchta hai aur guzar nahi paata. (d) mein positive terminal baayein hai, current triangle ki disha mein behta hai, aur LED jalta hai.

9. + aur − nishaan padhe nahi ja rahe. Terminal kaise pehchaanein? Cell ka chhoti ubhri dhaatu ki topi waala sira positive aur chapta sira negative hai. LED se bhi pata kar sakte ho: use battery se jodo; jale to LED ke lambe taar se juda terminal positive hai. Na jale to taar badlo: ab jalna chahiye, aur lamba taar positive terminal dikhaayega.

10. Cells A se F mein se kaunse chal rahe hain?

• (i) Saamaan: holder mein laga ek torch lamp (jo theek ho), ek cell ka holder, aur do-teen jodne waale taar jinke sire chhile hon.
• (ii) Tareeka: cell holder, lamp aur taaron ka circuit banao. Cell A holder mein lagaao; lamp jale to cell A chal raha hai, na jale to khatm ho chuka hai. Use nikaalkar B, C, D, E aur F ke saath doharaao, har baar wahi lamp aur taar. Pehle lamp ko kisi achhe cell se jaanch lo, taaki bujha lamp khatm cell ki nishaani ho, fuse lamp ki nahi.
• (iii) Activity karke har nateeja likho, jaise: A se lamp jala (chal raha), B se nahi jala (nahi chal raha), aur aage.

11. Kya Tanya ka LED jalega? Nahi. Dono cells ek hi taraf mukh kiye hain aur kaala taar unke negative terminals jodta hai, isliye cells ek doosre ke khilaaf dhakelte hain aur ek doosre ko kaat dete hain; current nahi behta. Sahi karne ke liye ek cell ulta karo aur ek cell ka positive terminal doosre ke negative terminal se jodo. Phir bache hue positive terminal ko LED ke lambe taar se aur bache hue negative terminal ko chhote taar se jodo.

Exploratory Projects (pages 39–40)

Do din bijli na ho to kya nahi kar paaoge? Ek namoona list: pankha, cooler ya AC nahi; andhera hone pe torch aur mombatti ke alaawa roshni nahi; Wi-Fi router band hote hi TV aur internet nahi; phone ki battery khatm; kai gharon mein nal ka paani nahi, kyunki pump nahi chalega; fridge nahi, isliye khaana kharaab; washing machine, mixer, press ya geyser nahi; oonchi imaaraton mein lift nahi; aur online class aur kaam ruk jaayenge.

Solar panel aur khilauna pankha. Solar panel ke do taar khilaune pankhe ki motor ke do terminals se jodo aur panel dhoop mein rakho; pankha ghoomega. Extra: agar ulti disha mein ghoome, to dono taar badal do.

Bijli ki dukaan pe cells (namoona report). Torch, remote, ghadi aur khilaunon ke liye AA cells; remote aur wireless mouse ke liye chhote AAA cells; badi torch aur radio ke liye bade C aur D cells; smoke alarm aur kuch khilaunon ke liye 9 V ki chaukor battery; ghadi, calculator aur sunne ki machine ke liye button cells; phone, laptop aur power bank ke liye rechargeable batteries; aur inverter aur gaadiyon ke liye badi lead-acid batteries.

Ghar ki cheezein teen samoohon mein (namoona). Sirf insulator: lakdi ka chammach, plastic ki baalti, rubber ki chappal, kaanch ka gilaas, kaagaz. Sirf conductor: steel ka chammach, lohe ki keel, aluminium foil, chaabiyan, steel ki thaali. Dono se bani: bijli ki press (dhaatu ka base, plastic ka handle), screwdriver (steel ki nok, plastic ka handle), pressure cooker (steel ki body, plastic ka handle), bijli ke taar (andar copper, bahar plastic) aur plug (dhaatu ki pins, plastic ka top).