Which statement describes a diode's current–voltage behavior?

Which statement describes a diode's current–voltage behavior?

• A. The current is not proportional to voltage; diodes do not obey Ohm's Law
• B. The resistance remains constant
• C. Diodes conduct equally in both directions
• D. The diode behaves exactly like a resistor

Answer: (A)

Diodes are non-linear devices: their current–voltage relationship is not a straight line like a resistor. Ohm’s law applies to elements with a constant resistance, giving a proportional, linear I–V relation. A diode, on the other hand, conducts mainly in the forward direction and only after a forward voltage is reached (about 0.6–0.7 V for silicon); once that threshold is passed, current rises very rapidly with only small increases in voltage. In reverse bias, the current is extremely small until breakdown. Because the current does not scale linearly with voltage and the device behaves differently in opposite directions, it does not obey Ohm’s law in the usual sense. That’s why the statement about current not being proportional to voltage captures the correct behavior. The other ideas—constant resistance, equal conduction in both directions, or behaving like a resistor—don’t fit how a diode actually behaves.

Diodes are non-linear devices: their current–voltage relationship is not a straight line like a resistor. Ohm’s law applies to elements with a constant resistance, giving a proportional, linear I–V relation. A diode, on the other hand, conducts mainly in the forward direction and only after a forward voltage is reached (about 0.6–0.7 V for silicon); once that threshold is passed, current rises very rapidly with only small increases in voltage. In reverse bias, the current is extremely small until breakdown. Because the current does not scale linearly with voltage and the device behaves differently in opposite directions, it does not obey Ohm’s law in the usual sense. That’s why the statement about current not being proportional to voltage captures the correct behavior. The other ideas—constant resistance, equal conduction in both directions, or behaving like a resistor—don’t fit how a diode actually behaves.