Question

Shown below is a graph of current versus applied voltage for a diode. Approximately what is the resistance of the diode for an applied voltage of $−1.5\,V$?

• A. Zero
• B. $1Ω$
• C. $2Ω$
• D. $∞$

Answer 1

Answer: (D)

The graph of current versus applied voltage for diode

In this case, at $-1.5\, V$, current in the circuit is zero. Hence, according to Ohm's law,
$R=\frac{V}{l}=-\frac{1.5}{0}=\infty$
Alternate Method
Consider the current versus applied voltage graph given in the question. It is clear from the graph that the current flowing through the diode is zero at a voltage of $-1.5\, V$. Therefore, the diode is reverse biased at this voltage. As we know that, infinite resistance is offered by a diode in reverse biased condition. Thus, given diode has infinite $(\infty)$ resistance for the applied voltage of $-1.5\, V$