Identify the barrier potential condition when p-n diode is forward bias.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1-No battery, 2-low voltage battery, 3-high voltage battery
The applied forward voltage \( V \) acts against the built-in potential \( V_0 \), so the effective barrier height under forward bias is \( V_0 - V \). The larger the forward voltage, the lower the barrier.
Curve 1: the highest barrier, the full \( V_0 \), so no battery is connected
Curve 2: the barrier is lowered a little, so a low voltage battery is connected
Curve 3: the barrier is lowered most, so a high voltage battery is connected
NCERT (2026-27):
p-n Junction Diode Under Forward Bias – “… As a result, the depletion layer width decreases and the barrier height is reduced [Fig. 14.13(b)]. The effective barrier height under forward bias is (V0 – V ). … If we increase the applied voltage significantly, the barrier height will be reduced and more number of carriers will have the required energy.”
