A standard 100 W 120 V lightbulb contains a 700 cm long tung

A standard 100 W (120 V) lightbulb contains a 7.00 cm -long tungsten filament. The high-temperature resistivity of tungsten is 9.0x10^-7 Ohm m. Part A What is the diameter of the filament? Express your answer with the appropriate units.

Solution

P = VI

I = 100/120 = 0.833 amp.

R = V/I = 120/0.833 = 144.05 ohm

R = rho*L/A

r = sqrt(9*10^-7*7*10^-2/(3.14*144.05)) = 0.118*10^-4 m

d = 0.236*10^-4 m