What is the Correct Definition of Dynamic Resistance and Resistivity?

[tiny-tim]

I'm confused about dynamic resistance.

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

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

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

is it ρ_d = d(Iρ)dI = ρ + I dρ/dI ?

 

[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.

 

[waht]

Here is a nice article

www.analogzone.com/col_0503.doc

 

[Redbelly98]

If R_D = dV/dI, then a reasonable definition for dynamic resistivity would be

ρ_D = dE/dJ,​

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