The experimental circuit arrangements for studying V-I characteristics of a p-n junction diode are given below:
Identify the circuit for forward bias and for reverse bias.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Circuit (i) reverse bias circuit (ii) forward bias
A p-n junction is forward biased when the p side is connected to the positive terminal of the battery (through the circuit) and the n side to the negative terminal. It is reverse biased when the connections are the other way round.
Circuit (i): the positive terminal of the battery (marked +) is joined through the microammeter and the resistor to the n side of the diode, and the p side goes back to the negative terminal. The n side is at the higher potential, so the diode is reverse biased.
Circuit (ii): the positive terminal is joined through the key to the p side, and the n side goes through the resistor and the milliammeter to the negative terminal. The p side is at the higher potential, so the diode is forward biased.
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 Reverse Bias – “When an external voltage (V) is applied across the diode such that n-side is positive and p-side is negative, it is said to be reverse biased [Fig.14.15(a)].”