# Dynamic resistance

1. Mar 30, 2009

### tiny-tim

The definition I've seen is Rd = dV/dI.

Is it also ok to write it Rd = d(IR)/dI, so that Rd = R + I dR/dI ?

I couldn't find a straightforward definition for dynamic resistivity at all …

is it ρd = d(Iρ)dI = ρ + I dρ/dI ?

2. Mar 30, 2009

### Bob S

Dynamic resistance is dV / dI. It is often used to refer to the dynamic forward resistance of a diode junction, or the dynamic resistance of a zener diode junction.

3. Mar 30, 2009

### waht

4. Mar 30, 2009

### Redbelly98

Staff Emeritus
If RD = dV/dI, then a reasonable definition for dynamic resistivity would be
ρD = dE/dJ,​

where E is electric field and J is the current density.