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**current and Ohm's Law--filament diameter**

## Homework Statement

A standard 100 W (120 V ) lightbulb contains a 8.50 cm -long tungsten filament. The high-temperature resistivity of tungsten is 9.0*10^-7.

## Homework Equations

Power=I[tex]\Delta[/tex]V=[tex]\Delta[/tex]^2/R

J=I/A

## The Attempt at a Solution

I know power, [tex]\Delta[/tex]V, and R and am solving for either r or d.

I can use the first equation to solve for I. And then I want to use the second equation because it is the only equation that I've found that uses area (and thus r and d), but I don't know J. Any suggestions? Thanks!