Determine the cross-sectional area of a tungsten filament in an electric lamp
| February 10, 2021 | education
Determine the cross-sectional area of a tungsten filament in an electric lamp if the filament is 100 mm long and its cold resistance is 27.5 ohms.
Initial data: l (length of tungsten filament) = 100 mm (0.1 m); R (cold resistance of the tungsten filament) = 27.5 ohms.
Constants: ρ (electrical resistivity of tungsten) = 0.055 Ohm * mm2 / m.
The cross-sectional area of the taken tungsten filament is determined from the formula for calculating the resistance of the conductors: R = ρ * l / S, whence S = ρ * l / R.
Calculation: S = 0.055 * 0.1 / 27.5 = 0.0002 m2 (200 mm2).
Answer: The tungsten filament has a cross-sectional area of 200 mm2.
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