MadSci Network: Physics

Re: how can you overcome the heating effect?

Date: Tue May 1 20:25:19 2001
Posted By: Michael L. Roginsky, Staff, Avionics, Honeywell Defense Avionics
Area of science: Physics
ID: 987774886.Ph

Hello Michelle: Pure metals such as silver, copper and aluminum have a 

positive coefficient of resistance versus temperature meaning that as the 

temperature of the conductor increases so does the resistance. Your wire 

samples must be physically the same to perform the experiment you 

described. Notice that the change in resistance of a piece of wire is not 

very large requiring sensitive equipment to be used in the demonstration. 

Take two cheap Radio Shack resistors of equal value, for example, 1000 

ohms each, connect them in series to a 6-volt battery. Each will drop of 3 

volts more or less because of the resistance tolerances. After taking the 

room temperature reading across one with a voltmeter, apply warm air from 

a hair dryer. As the resistor gets hot, the voltage across it will rise 

indicating the resistance value increases. Be sure you have good 

connections between the resistors and the battery as well. The voltage 

change will not be dramatic. Look-up this reference on the Internet:

Your MAD.SCI Micro.

Question submitted on Fri Apr 20 09:54:46 2001.
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