An unbiased p-n junction diode has barrier potential of 0.7 V. Arrange the barrier potentials in increasing order of their values under the following situations.
(A) Reverse biased with voltage 0.7 V
(B) Reverse biased with voltage 1.5 V
(C) Forward biased with voltage 0.5 V
(D) Forward biased with voltage 0.7 V
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (D), (C), (A), (B)
The applied voltage changes the height of the potential barrier of a p-n junction. Forward bias opposes the barrier and lowers it by the applied voltage; reverse bias adds to it.
\( \text{(A) } 0.7\,\mathrm{V} + 0.7\,\mathrm{V} = 1.4\,\mathrm{V} \)
\( \text{(B) } 0.7\,\mathrm{V} + 1.5\,\mathrm{V} = 2.2\,\mathrm{V} \)
\( \text{(C) } 0.7\,\mathrm{V} - 0.5\,\mathrm{V} = 0.2\,\mathrm{V} \)
\( \text{(D) } 0.7\,\mathrm{V} - 0.7\,\mathrm{V} = 0 \)
Increasing order: (D), (C), (A), (B).
NCERT (2026-27):
p-n Junction Diode Under Forward Bias – “… The effective barrier height under forward bias is (V0 – V ).”
p-n Junction Diode Under Reverse Bias – “… The effective barrier height under reverse bias is (V0 + V ), [Fig. 14.15(b)].”