# Temperature a current

1. Jul 10, 2010

### randomss444

1. The problem statement, all variables and given/known data

Is current different at different temperatures, as it heats up to its working temperature?

2. Relevant equations

3. The attempt at a solution

My answer would be no because current does not change.

Is that correct?

2. Jul 10, 2010

### xcvxcvvc

Temperature changes resistance of materials.

3. Jul 10, 2010

### randomss444

Alright so that means that current is effected by temperature because in order to find current you need to know resistance and because resistance is effected by temperature. Correct?

4. Jul 10, 2010

### xcvxcvvc

Yeah. The actual parameter that changes with temperature is called conductivity or resistivity (they are reciprocals of each other). The less temperature you have, the less kinetic energy you have. So the electrons, when a voltage is applied, move straight to where they want to go easier and without interference as you approach absolute zero temperature. However, when you add the kinetic energy (the heat), the electrons can no longer smoothly move to where the voltage attracts them to. Instead, they bounce around crazily, often in the opposite direction as the voltage demands, but with an overall "drift" toward the "right" direction. This effect becomes greater and greater as you increase the temperature.

$$\sigma = q(n\mu_n + p \mu_p)$$
where sigma is conductivity and the mu_n and mu_p are electron and hole mobilities respectively. The mobility is a numerical estimate that contains the effects that I described earlier about temperature. n and p are the electron and hole concentrations. q is the charge of a proton.

In case you did not know, resistance is directly proportional to resistivity and inversely proportional to its reciprocal, conductivity.

5. Jul 10, 2010

### Redbelly98

Staff Emeritus
I can't believe that is the full problem statement. The current of what? If you mean something that is connected to a constant-current source, then the current would be the same at different temperatures.