How does Temperature affect Resistance?

[roxychc43]

Homework Statement

What is the effect of temperature on resistance? I was given an experiment to test this out... I was told to use a cylindrical bulb, a socket, connecting wires, DC power supply, ammeter, and a voltmeter. I was to connect the DC power supply to one end of the ammeter via connecting wires and the other end of the ammeter was to connect to the light bulb via connecting wires. The other end of the light bulb is supposed to be connected to the DC power supply via connecting wires... now that I have a complete circuit I was told to turn on the power supply and increase the voltage in .5 increments, taking corresponding measurements of current, but not to exceed 8 volts. I was then supposed to put my data in a table and plot a graph of voltage as a function of current.

And when I put the data into the graph it is a curve.. What would be the best fit equation for this curve? A power, exponential, Log?

I am also supposed to determine the mathematical expression that describes the change in resistance as a function of temperature. I am also supposed to find the theoretical expression that describes that relationship and then determine the experimental resistivity of the bulb filament. It tells me to look up what material is used for bulb filaments, and compare the theoretical resistivity to my measured value.

Homework Equations

V=IR

I think the mathematical expression that describes the change in resistance as a function of temperature is

Rt=Rr(1 + alpha (deltaT))

and I know that Tungsten has a temperature coefficient of 5.6 x 10^-8

The Attempt at a Solution

-What seems to be happening to the resistance of the bulb as the current increases?
The resistance increases because according to the equation V=IR as the voltage increases the current increases.
-What do you think the reason is for this effect? Explain Clearly
I'm not to sure other than temperature? can you help explain why?

I don't know anything about the bulb other than it is a little cylindrical one and I don't know the cross-sectional area.

 

[LowlyPion]

You might find this lecture useful at about 17 minutes or so. (Actually the whole thing is interesting, but in particular as to your heat /resistance question.)