# Temperature of Bulb Filament

by JJones_86
Tags: bulb, filament, temperature
 P: 72 1. The problem statement, all variables and given/known data A common flashlight bulb is rated at 0.3 A and 3.3 V (the values of current and voltage under operating conditions). If the resistance of the bulb's tungsten filament at room temperature (20.0 degrees Celsius) is 1.10 Ohms , estimate the temperature of the tungsten filament when the bulb is turned on. Take the temperature coefficient of resitivity for tungsten to be 4.5e10-3 2. Relevant equations R = V/I 3. The attempt at a solution R = 3.3V / 0.3A = 11 Ohms when turned on Little lost on how to find the temperature when turned on.
 PF Patron HW Helper P: 3,394 What are the units on that coefficient of resistivity? Perhaps we can make up a formula relating it to temperature and resistance.
 P: 1,760 I'm curious about a custom I see universally in this forum. It's been quite a few years since I was in school and I wonder if this custom indicates a change in the way EE is being taught nowadays. Traditionally E instead of V has been used to represent electromotive force just as I represents current instead of A. In the past a distinction has been made between the unit of electromotive force and its designator. Are instructors and textbooks now using V for electromotive force?
HW Helper
P: 5,346

## Temperature of Bulb Filament

How much does the resistance of the filament change?

With that Δ in resistance perhaps you can figure the Δ in temp needed to develop that much resistance?
PF Patron
HW Helper
P: 3,394
 Traditionally E instead of V has been used to represent electromotive force
I remember that, Skeptic! I've been in high school for 30 years and all our books and government exams just used V for electric potential, which is a bit confusing leading inevitably to saying "Voltage" instead of "potential". But P and E are busy already so V is a relief.
 P: 13 Problem is ez. You have found the R. That's good! Look at this website to know more about the coefficent. You will figure out. http://hyperphysics.phy-astr.gsu.edu...ic/restmp.html

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