Non-linear, asymmetric V-I curve identifies diode

Steps:

• Examine graph for linearity: straight line indicates ohmic device, curve indicates non-ohmic.
• Check symmetry: forward and reverse bias behavior differs in diodes.
• Compare to standard curves: diode shows exponential rise in forward bias, negligible current in reverse.
• Eliminate linear options to confirm non-ohmic, directional component.

Why D is correct:

• Semiconductor diode follows Shockley equation, I = I_s (e^(V/(nV_T)) - 1), yielding exponential forward current and blocking reverse current.

Why the others are wrong:

• A. Filament lamp: Non-linear due to heating but symmetric and ohmic at low currents.
• B. Metal conductor at constant temperature: Linear through origin per Ohm's law, V = IR.
• C. Resistor: Strictly linear, constant resistance per Ohm's law.

Final answer: D