A cylindrical tungsten filament 14.0 cmcm long with a diameter of 1.00 is to be used in a machine for which the temperature will range from room temperature (20 ∘C∘C) up to 120 ∘C∘C. It will carry a current of 14.0 AA at all temperatures ( Resistivity of tungsten at 20 ∘C∘C is

Resistivity ρ=1.12 x 10^-4 Ωm

Explanation:

ρ= RA/l, where R is resistance, A is cross sectional area and l is length

A=πr^2

Note Current is given R is proportion to temperature and inversely proportional to Current R=(20+273)/14*10^-2 =2000Ω

⇒ρ=R*πr^2/l all length in metre.

mistakes are ok