Forward And Reverse Bias

Question

A junction diode is connected so that its p-side goes to the positive terminal of a battery and its n-side to the negative terminal of the same battery.

RankGuru · Accepted Answer

NCERT describes forward bias as connecting the p-side to the positive terminal and the n-side to the negative terminal of a battery. The applied voltage opposes the internal barrier field, so the barrier potential is lowered and the depletion region becomes thinner. Once the applied voltage exceeds the knee or threshold value, majority carriers cross the junction easily and a large forward current flows, so the diode conducts strongly. The option describing a widening depletion width belongs to reverse bias, where the external field aids the barrier, so it is wrong here. The option about an increasing barrier and no diffusion again describes reverse bias and contradicts the given forward connection. The option that the diode acts like an open switch is wrong because a forward-biased diode behaves like a closed switch with low resistance, not an open one. As stated in NCERT Class 12, Chapter 14, forward bias reduces the barrier and depletion width, allowing conduction. A consistency check confirms the current rises sharply beyond the threshold, matching the exponential diode characteristic near the knee voltage.

Forward And Reverse Bias

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