Write the formula and definition of dynamic resistance and also state their approximate values for forward bias and reverse bias.

(N/A) Dynamic resistance $(r_d)$ is defined as the ratio of a small change in voltage $(\Delta V)$ to the corresponding small change in current $(\Delta I)$ across a diode.
Formula: $r_d = \frac{\Delta V}{\Delta I}$.
For forward bias, the dynamic resistance is very low, typically in the range of $1 \, \Omega$ to $25 \, \Omega$.
For reverse bias, the dynamic resistance is very high, typically in the range of $10^5 \, \Omega$ to $10^6 \, \Omega$.