# Voltage and resistance

1. Dec 15, 2014

### sunwoo lee

recently, I did a experiment about insulating coating on a powder.

and I measured resistance with various voltage.

according to Ohm's law, the resistance is constant

however, my sample showed different resistance with difference V.

At every voltage, I checked the currents and the resistance and their multiplies(I*R) show same voltages.

Is it possible that resistance changes?

Please, explain me if anyone can...

Last edited by a moderator: Dec 22, 2014
2. Dec 15, 2014

### Bystander

Can you post your raw data? V, i, R?

3. Dec 15, 2014

### CWatters

It is possible. Take a look a the IV curve for a diode. At different voltages the slope of the curve changes.

4. Dec 15, 2014

### Vagn

Even for a simple wire, Ohm's law won't always hold. As you increase the current and voltage, at some point the I-V curve will become non-linear due to the wire heating up.

5. Dec 15, 2014

### sophiecentaur

Ohm's law actually stipulates constant temperature. People confuse Ohm's Law with the simple formula for Resistance (=V/I). There is a distinct difference, of course.

6. Dec 15, 2014

### ImperialThinker

The temperature should be constant. I did not clearly understand your experiment, more detail please ?