Under forward-bias of a p-n diode
(A) p-side of the diode is connected to the positive terminal of the battery and n-side to the negative terminal
(B) p-side of the diode is connected to the negative terminal of the battery and n-side to the positive terminal
(C) The direction of the applied voltage (V) is opposite to the built-in potential drop
(D) The direction of the applied voltage (V) is the same as the built-in potential drop
(E) The magnitude of the diode forward current is usually in mA
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A), (C) and (E) only
(A) p-side of the diode is connected to the positive terminal of the battery and n-side to the negative terminal. — Correct. This is the definition of forward bias.
(B) p-side of the diode is connected to the negative terminal of the battery and n-side to the positive terminal. — Incorrect. This connection is reverse bias.
(C) The direction of the applied voltage (V) is opposite to the built-in potential drop. — Correct. The applied voltage opposes the built-in potential, so the depletion layer narrows and the barrier height falls.
(D) The direction of the applied voltage (V) is the same as the built-in potential drop. — Incorrect. That is the case for reverse bias; in forward bias the two are opposite.
(E) The magnitude of the diode forward current is usually in mA. — Correct. The forward current of a junction diode is of the order of milliamperes.
NCERT (2026-27):
p-n Junction Diode Under Forward Bias – “When an external voltage V is applied across a semiconductor diode such that p-side is connected to the positive terminal of the battery and n-side to the negative terminal [Fig. 14.13(a)], it is said to be forward biased.”
p-n Junction Diode Under Forward Bias – “… The direction of the applied voltage (V ) is opposite to the built-in potential V0.”
p-n Junction Diode Under Forward Bias – “… The total diode forward current is sum of hole diffusion current and conventional current due to electron diffusion. The magnitude of this current is usually in mA.”