The Heating of Nichrome Wire in a toaster

  • Thread starter gc33550
  • Start date
  • #1
22
0

Homework Statement



A toaster with a Nichrome heating element has a resistance of 70 ohms at 20oC and an initial current of 1.6 A. When the heating element reaches its final temperature, the current is 1.39 A. What is the final temperature of the heating element?

Homework Equations



V=IR
[tex]\alpha[/tex]=([tex]\rho[/tex]-[tex]\rho[/tex]o)/[tex]\rho[/tex]/(Tf-To)

The Attempt at a Solution


I know that the voltage will remain constant therefore:
Io*Ro=If*Rf
I also know that Nichrome's [tex]\alpha[/tex]=100e-8
but I don't really know where to go from here
 

Answers and Replies

  • #2
2,014
289
from [tex]

\alpha = \frac {\rho - \rho_0} {\rho} (T_f - T_0)

[/tex]

try to derive an equation for R as a function of R_0, T_0, T_f and [itex] \alpha [/itex]
you know the new R from ohms law.

The temperature coefficent of nichrome is [itex] 4 *10^{-4} K^{-1} [/itex]
 
  • #3
22
0
So am I going to be looking at resistivity then? such as [tex]\rho[/tex]=R*A/L ??
 
  • #4
2,014
289
So am I going to be looking at resistivity then? such as [tex]\rho[/tex]=R*A/L ??

yes. Instead of [tex]\rho[/tex]=R*A/L you can use [tex]\rho[/tex]=R*C. You don't know what A and L are anyway, except that they are constant.
 
  • #5
22
0
C as in capacitance? How do I find that?
 
  • #6
2,014
289
C as in capacitance? How do I find that?

no it's just an arbitrary constant
 
  • #7
22
0
would that constant be in my physics book somewhere?
 

Related Threads on The Heating of Nichrome Wire in a toaster

  • Last Post
Replies
1
Views
2K
Replies
20
Views
3K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
1
Views
6K
  • Last Post
Replies
12
Views
3K
Replies
3
Views
60
  • Last Post
Replies
1
Views
513
Replies
2
Views
1K
  • Last Post
Replies
8
Views
12K
  • Last Post
Replies
2
Views
3K
Top