If the 0.100-mm-diameter tungsten filament in a light bulb is to have a resistance of 0.300 \OmegaΩ at 20.0 ^o
o
C , how long should it be?
The length is given as follows:
where is the area of the filament cross-section, is the diameter, is the resistance, and is electrical resistivity of tungsten. Thus, obtain:
Answer. 4.21 cm.
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