Answer:
Length L=0.0125 m
Explanation:
Given data
Resistance R=0.11Ω
Temperature T=20°C
Resistivity of tungsten at 20°C p=5.6×10⁻⁸Ω.m²
Radius of filament r=0.09/2 =0.045 mm =0.045×10⁻³m
To find
Length of filament L
Solution
The Cross section of area of filament is given as:
[tex]A=\pi r^{2}\\ A=\pi (0.045*10^{-3})^{2}\\A=6.3585*10^{-9}m^{2}[/tex]
The Resistance of a material is given as:
[tex]R=p\frac{L}{A} \\L=\frac{AR}{p}\\ L=\frac{(6.3585*10^{-9})(0.11)}{5.6*10^{-8}}\\L=0.125m[/tex]
