# Homework Help: Temperature to raise resistance

1. Sep 16, 2010

### Spoonerz

1. The problem statement, all variables and given/known data
A platinum wire is originally at 15 degree Celcius. Find the required temperature to increase its resistance by 3%.

2. Relevant equations
R = Ro * [1 + 'a' * (T-To)]
Ro is initial resistance. To is initial temperature.
'Temperature Coefficient' 'a' of platinum at room temperature 20 degree celcius is 3.9 * 10^-3

3. The attempt at a solution
I don't have an initial resistance to start off with. But I do have the initial temperature and the room temperature, To = 15 and T = 20 degree Celcius.

Solving for Temperature T = ('a'To + R/Ro) / 'a'
But I don't have any reference resistance to begin with, how do I solve this?

2. Sep 16, 2010

### xcvxcvvc

$$R = R_o[\alpha (T - T_o) + 1]$$
$$R = 1.03R_o$$

3. Sep 16, 2010

### Spoonerz

Can you show how you got this by eliminating all the other variables? Even from this simplified form, there isn't an initial resistance to begin with. Unless....

$$R_o = R / 1.03$$

?