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Answer: A cylindrical tungsten filament 15.0 cm long with
Chapter 25, Problem 15E(choose chapter or problem)
Problem 15E
A cylindrical tungsten filament 15.0 cm long with a diameter of 1.00 mm is to be used in a machine for which the temperature will range from room temperature\(\left(20^{\circ} \mathrm{C}\right)\) up to \(120^{\circ} \mathrm{C}\). It will carry a current of 12.5 A at all temperatures (consult Tables 25.1 and 25.2). (a) What will be the maximum electric field in this filament, and (b) what will be its resistance with that field? (c) What will be the maximum potential drop over the full length of the filament?
Equation Transcription:
Text Transcription:
(20degC)
120degC
Questions & Answers
QUESTION:
Problem 15E
A cylindrical tungsten filament 15.0 cm long with a diameter of 1.00 mm is to be used in a machine for which the temperature will range from room temperature\(\left(20^{\circ} \mathrm{C}\right)\) up to \(120^{\circ} \mathrm{C}\). It will carry a current of 12.5 A at all temperatures (consult Tables 25.1 and 25.2). (a) What will be the maximum electric field in this filament, and (b) what will be its resistance with that field? (c) What will be the maximum potential drop over the full length of the filament?
Equation Transcription:
Text Transcription:
(20degC)
120degC
ANSWER:
Solution 15E
We shall have to first calculate the resistivity of the tungsten filament using the equation of resistivity dependence on temperature …..(1), where is the resistivity at a reference temperature, is temperature coefficient of resistivity and is the difference of temperature.
Given in the question,
Length of the filament
Diameter of the filament
Radius
Therefore, area of the filament
Current
Therefore, current density