Question
A toaster uses a Nichrome heating wire. When the toaster is turned on at 20°C, the initial current is 1.50 A. A few seconds later, the toaster warms up and the current has a value of 1.22 A. The average temperature coefficient of resistivity for Nichrome wire is 4.5 10-4 (C°)-1. What is the temperature of the heating wire?
Answers
The relative change in resistivity as the wire heats up is 1.50/1.22 = 1.2295. That is a 22.95% INCREASE.
(delta T)* coefficient of resistivity = 0.2295
delta T = 0.2295/4.5*10^-4 = 510 C
T = 510 + 23 = 533 C
(delta T)* coefficient of resistivity = 0.2295
delta T = 0.2295/4.5*10^-4 = 510 C
T = 510 + 23 = 533 C
where are you getting 22.95% and what is delta T
R = V/i , V is constant here
V/i2 = V/i1 (T2-T1)k
i1 = i2 (T2 - 20) k
1.5 = 1.22 (T2 - 20)(4.5 * 10^-4)
15000 = 5.49 T2 - 110
You can get it from there
V/i2 = V/i1 (T2-T1)k
i1 = i2 (T2 - 20) k
1.5 = 1.22 (T2 - 20)(4.5 * 10^-4)
15000 = 5.49 T2 - 110
You can get it from there
Whoa - I forgot the definition. dr wls did it right !
In answer to your followup questions: delta T is the increase in temperature. The 22.95% resistance increase was explained in my first calculation. 1.2295 is the inverse of the current decrease factor, 1.22/1.50. Since I = V/R, the current varies inversely with the resistance at constant voltage
drwls is correct. To get the percentage subtract 1.22 from 1.5, then divide by 1.22
Related Questions
The heating elements of an electric toaster is typically made of nichrome wire
(an alloy of nickel...
A toaster draws 12 A of current when plugged into a 110 V outlet. The toaster coils glow red
hot wh...
Why is the toaster able to destroy LOONY GOONY? (The brave little toaster)
• The toaster is braver...