Ohm’s law

Theory

What happens to current when you change the voltage? In an ohmic conductor, V and I rise in the same proportion while temperature stays constant. Their ratio is the resistance R. This pattern applies to some components, not all of them.

Plot I in amperes along the horizontal axis and V in volts along the vertical axis. An approximately straight line through the origin shows nearly constant resistance. Find R from the slope ΔV/ΔI, in ohms. A warming resistor may change resistance, so watch for a curve instead of a straight line.

V = IR

Use volts for V (potential difference), amperes for I (current), and ohms (Ω) for R (resistance).