Which statement about diodes is false?

• A. Diodes pass current only in one direction.
• B. Diodes behave like a small resistor when forward biased.
• C. The forward voltage drop is small but nonzero.
• D. Diodes are used to rectify AC.

Answer: (B)

Diodes are nonlinear devices whose current-versus-voltage behavior isn’t like a simple resistor. In forward bias, they turn on abruptly: a small forward voltage is required, and once conduction starts, current rises rapidly with only modest changes in voltage. That steep, non‑linear relationship means a forward-biased diode does not behave like a small resistor with a fixed V=IR. The idealized view is that the forward voltage stays around a small, nonzero value (roughly 0.7 V for silicon) while current increases, rather than the voltage being proportional to current as a resistor would.

So, the statement that diodes behave like a small resistor when forward biased is not accurate. The other points reflect common diode behavior: they conduct primarily in one direction, the forward drop is small but nonzero, and they are used to rectify AC by passing current in one half-cycle and blocking it in the other.