A thermometer can be made from a brass wire (temperature coefficient of resistiv

Question

A thermometer can be made from a brass wire (temperature coefficient of resistivity 0.00150°C-1 at 20.0°C) which has a potential difference of 1.50 V between its ends and is connected to an ammeter. A measurement determines that the current flowing through the wire is 347 mA when the wire is at room temperature (20.0°C). (a) What is the resistance of the wire? (b) What change in current will accompany a decrease in temperature of one degree Celsius (or one kelvin)? Be careful of the sign of your answer.
(the answer to a. is 4.32...i need major help for part b though)

Explanation / Answer

a) R = V/I = 1.50 / 347 x 10^-3 = 4.32 O b) let's calculate the change in resistance with 1 degree fall in tempertaure R = Ro ( 1 + a{T-To})    where Ro is the original resistance, a = temperature coefficient                                     T = new temperature, To = old temperature Plugging the values, we get R = 4.32 ( 1 + 0.00150{ 19-20}) solving for R, R = 4.32 ( 1 -0.00150) R= 4.31352 O approx Current = V/R = 1.50/ 4.31352= 0.347744 A approx I= 348 mA approx

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