1. A 1.3 cm length of tungsten filament in a small lightbulb has a resistance of 0.032 ohms. Find its diameter. Given: Length= 1.3 cm= .013m R= 0.032 ohms resistivity= 5.6e-8 ohms*meter 2. A= pi (r^2) R= resistivity (Length/ Area) 3. The attempt at a solution R= resistivity ( Length/ pi* (r^2) ) .032 ohms= (5.6e-8 ohms*meter) * (.o13m/ (pi* (r^2)) ) .032 (pi) (r^2) = 7.28e-10 .100530965 (r^2) = 7.28e-10 r= 8.509e-5 diameter= 2r= 1.701e-4m It asks for the answer in mm, so I divided my answer by 1000= 1.7 e-7 mm, but it's not correct = ( What am I missing? Thanks in advance!