The I-V characteristics of a p-n junction diode in forward bias is shown in the figure. The ratio of dynamic resistance, corresponding to forward bias voltage of 2 V and 4 V respectively, is :

CONCEPT:

• According to Ohm's law, the applied voltage is directly proportional to the current flow in the given circuit and it is written as;

          V = IR

           R = \(\frac{V}{I}\)

          Here we have R as resistance, V as the applied voltage, and I as the current.

• For the given graph the dynamic resistance is written as;

           R = \(\frac {\Delta V}{\Delta I}\)

CALCULATION:

From the above graph the voltage of 2V, the dynamic resistance is written as;

R₁ = \(\frac {\Delta V_1}{\Delta I_1}\)

⇒ R1 = \(\frac {2.1 - 2}{10 -5}\)

⇒ R₁ = 0.02 Ω       ----(1)

Similarly, 

From the above graph the voltage of 4V, the dynamic resistance is written as;

R2 = \(\frac {\Delta V_2}{\Delta I_2}\)

⇒ R₂ = \(\frac {4.2 - 4}{250 -200}\)

⇒ R₂ = 0.004 Ω     ----(2)

Now, On dividing equation (1) by (2) we have:

\(\frac{R_1}{R_2} \) = \(\frac{0.02}{0.004}\)

⇒ \(\frac{R_1}{R_2}\) = \(\frac{5}{1}\) = 5:1

Hence, option 2) is the correct answer.