Question

The filament of 50 W and 90 W bulbs are of the same length, then (a) 50 W filament is thicker (b) 90 W filament is thicker (c) both are of same thickness (d) none of these​

Answer 1

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Q-The filament of 50 W and 90 W bulbs are of the same length, then (a) 50 W filament is thicker (b) 90 W filament is thicker (c) both are of same thickness (d) none of these​

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(A)90 W filament is thicker

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We know that

R∝1/A                  -----(1)

P∝1/R OR R∝1/P  -----(2)

From Eq 1 and 2

1/P∝1/A

P∝A

So we can conclude that If a substance has more electrical power then it will also have more area of cross section

Here

P50 <P90

∴Filament of 90 W bulb is thicker than 50 W bulb

∴Option (a) is correct

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