A diode conducts in one direction and blocks in the other due to its directionality.

• A. Capacitance
• B. Inductance
• C. Resistance
• D. Directionality

Answer: (D)

Directionality is what makes a diode behave one way. A diode’s PN junction creates an asymmetrical current path: when forward biased, the depletion region narrows and carriers cross the junction, letting current flow with only a small forward voltage drop. When reverse biased, the depletion region widens and blocks most current, so the device acts like an insulator in that direction. This built-in one-way conduction is the defining feature of a diode.

The other options describe different electrical properties. Capacitance stores charge and governs charging and discharging of a circuit, not one-way current flow. Inductance resists changes in current due to magnetic field effects. Resistance is a general opposition to current that applies in both directions and doesn’t inherently enforce one-way conduction.