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Bulb, Circuit aur Switch

Class 7 Science · Chapter 3: Bijli: Circuit aur Unke Hisse · NCERT Curiosity section 3.2.3–3.2.6

Seekho

Puraane torch ka bulb incandescent hai: kaanch ke andar patla taar, filament, do mote taaron se thaama hai jo dhaatu ki nok aur dhaatu ke khol (bulb ke do terminal) se jude hain. Current filament ko garam karke chamkaata hai. Filament toote to bulb fuse ho gaya. Naye torch mein LED (light emitting diode) hote hain, jinmein filament nahi.

Kabir taaron se cell ko bulb se jodta hai. Bulb tabhi jalta hai jab bulb ka ek terminal cell ke ek terminal se, aur doosra doosre se jude. Ye poora raasta electrical circuit hai. Current cell ke + terminal se ghoomkar − tak behta hai. Filament bulb kisi bhi taraf jude, farak nahi.

LED ke do pair: lamba +, chhota −. LED mein current sirf ek disha mein jaata hai, isliye wo tabhi jalta hai jab uska + pair battery ke + se jude. Ulta karo to andhera. Chinh mein tikon us disha mein ishaara karta hai jidhar current ja sakta hai.

Ghar ka switch: drawing pin par ghoomti safety pin doosri drawing pin ko chhoo sakti hai. Chhoone par khaali jagah band: circuit band (ON) aur bulb jalta hai. Na chhoone par khaali jagah: circuit khula (OFF). Switch circuit mein kahin bhi lag sakta hai; ghar ke switch bhi aise hi kaam karte hain.

Explore: circuit theek karo.

  1. Switch aur LED aise set karo ki LED jale.

Yaad rakho

  • Bulb sirf poore circuit mein jalta hai; current + se − behta hai.
  • LED sirf ek taraf (lamba pair + par); switch circuit kholta ya band karta hai.

Quick check

Achchhi battery ke saath poore circuit mein LED nahi jalta. Pehle kya aazmaoge?

  1. LED ulto
  2. aur taar jodo
  3. battery hataao
  4. LED rango
Answer

LED ulto. LED mein current ek hi taraf: lamba pair + par jaana chahiye.

Socho

Ek upkaran mein cells aage-peeche nahi, agal-bagal hain. Phir bhi + se − kaise jude?

Ek answer

Khaane ke andar mota taar ya dhaatu ki patti ek cell ka + agle ke − se jodti hai; + aur − nishaan lagaane ka tareeka dikhaate hain.

Practice

Teen levels (easy, medium, hard) ke naye sawaalon se practice karo, kuch hands-on, hints aur hal ke saath. Topic poora karne ke liye pichhle 5 mein se 4 sahi karo.