Question

Are Resistors Ohmic Devices? Internet research tells me, they are. My graph says they are Non-Ohmic Devices.

I know that a diode, for instance, is an example of a Non-Ohmic Device because its graph is a curve. However, when I graphed some Voltages (y-axis) and Currents (x-axis) of a resistor, the result was a variation in slopes (which is also the resistance), meaning to say that the graph is not a straight line (even just by looking at the minute fluctuations). Despite that, is the resistor still considered Ohmic? The deviations are not as pronounced as it is in a diode's graph.

Answer 1

Resistors are ohmic. Ohm's law is generally true; however, every device will break down if it's internal electric field is high enough. The resistance of light bulbs, for example, increases with temperature and its V vs I curve is anything but linear, making it extremely non-ohmic. Diodes are designed to have extreme V vs I curves and are considered nonlinear devices for that reason.

The power ratings of resistors are important to observe in order to keep them in their linear or "ohmic" regions.

Answer 2

When I graphed this:

Current I (in mA) | Voltage Delta V (in Volts)
0 | 0
24.4 | 2.43
48.2 | 4.97
72.5 | 7.23
96.4 | 9.95

My graph was linear everywhere except at (72.5, 7.23).

So, is my resistor still considered Ohmic, or Non-Ohmic?

Also, do I use \[R=\Delta V/ \Delta I\] to solve for the Resistance or R=V/I?

Answer 3

I just graphed your data and it is very linear. I don't see a problem at <72.5,7.23>. It is slightly out from the regression line, but that could be accounted for in precision of the measurement tool.

Answer 4

Oh okay. That makes sense. Thanks for the help!

Answer 5

yw