Why are equivalent bulbs filled with chemically inactive nitrogen or argon gas? (b) The resistance of a wire of 0.01cm radius is 10 Omega. If the resistivity of the material of the wire is 50 times 10^-8 Omega.m Find the length of the wire.

Why are equivalent bulbs filled with chemically inactive nitrogen or a

1.	Why are equivalent bulbs filled with chemically inactive nitrogen or argon gas? (b) The resistance of a wire of 0.01cm radius is 10 Omega. If the resistivity of the material of the wire is 50 times 10^-8 Omega.m Find the length of the wire.
Answer» Solution :Electric bulbs are GENERALLY filled with some inert GAS like NITROGEN or argon. This enables to prolong the life of the filament of electric bulb. (b) Here radius of wire r=0.01 cm =`0.01 times 10^-2 m` resistance R=`10 Omega` and resistivity `rho=0 times 10^-8 Omega.m` As `R=(rho L)/A=(rho L)/( pi r^2)`, hence length `L=(R pi r^2)/( rho)` `implies L= (10 times 22 times (0.01 times 10^-2)^2)/(7 times 50 times 10^-8)=22/35 m=0.629m or 62.9 cm`