27. Resistors & DC Circuits
Resistors and Ohm's Law
10:14 minutes
Problem 25.26
Textbook Question
Textbook Question(III) The filament of an incandescent lightbulb has a resistance of 12 Ω at 20°C and 140 Ω when hot.
(a) Calculate the temperature of the filament when it is hot, and take into account the change in length and area of the filament due to thermal expansion (assume tungsten for which the thermal expansion coefficient is ≈ 5.5 10⁻⁶ C°⁻¹ ).
(b) In this temperature range, what is the percentage change in resistance due to thermal expansion, and what is the percentage change in resistance due solely to the change in ρ? Use Eq. 25–5.
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