Two electric bulbs marked 100W 220V and 200W 200V have tungsten filament of same length. Which of the two bulbs will have thicker filament?

We know, 

P = V2/R 

⇒More the power, lesser the resistance. 

The resistance of 200W bulb is lesser than the 100W bulb.


R = ρ l/A

⇒Higher the resistance,lesser will be the value of A. Thus, thinner will be the wire. 

The wire of 200W bulb is thicker than 100W bulb, as it's resistance is lesser.


P ∝A

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