Diode-Resistor Series Circuit I-V Characteristic

Steps:

• In series, total V = V_resistor + V_diode; current I is same through both.
• Diode conducts significantly only in forward bias (V > ~0.7V for silicon), blocking reverse current.
• For V < 0, I ≈ 0 due to diode reverse bias.
• For V > 0.7V, diode forward drop is nearly constant, so I ≈ (V - 0.7V)/R, linear with slope 1/R.

Why A is correct:

• Graph A shows I=0 for V<0, then linear increase for V>0.7V, matching diode threshold and resistor limiting current per Ohm's law.

Why the others are wrong:

• B: Linear through origin, ignores diode threshold, like resistor alone.
• C: Symmetric conduction, contradicts diode's rectification.
• D: Non-linear or reverse conduction, violates diode's one-way behavior.

Final answer: A