The V-I characteristic of a silicon diode is shown in the Fig. Calculate the resistance of the diode at
`I_D =15 mA `

Explanation

Considering the diode characteristics as a straight line between I = 10 mA to I = 20 mA passing through the origin, we can calculate the resistance using Ohm.s law.
From the curve, at I = 20 mA, V=0.8 V,
I= 10 mA, V=0.7 V
`r_(fb ) = Delta V// DeltaI =0.1V//10mA = 10 Omega `