Question

p-type crystal of p-n junction diode is connected to a positive terminal of the battery and n-type is connected to a negative terminal of the battery. Then
a) diode is forward biased
b) diode is reversed biased
c) potential barrier in depletion region increases
d) potential barrier in the depletion layer remains unchanged

Answer 1

Hint:In the above question, the information regarding how the diode is connected to the battery is given to us. The p-type crystal of the p-n junction diode is filled with positive charges and the n-type is filled with negatively charged electrons. Hence depending on how a battery is connected to the junction diode, the current will flow across the diode (in case of forward biased) or the current will not flow across the diode (in case of reversed biased).

Complete step-by-step solution:
Given below is a diagram of a p-n junction diode which is forward biased.

In the above question it is given that the p-type crystal of the p-n junction diode is connected to a positive terminal of the battery and n-type is connected to the negative terminal of the battery. The accumulation of negative charges in the p-region and the positive charges in the n-region sets up a potential difference across the junction. This is called the barrier potential. When the positive side of the battery is connected to the p-region and the negative terminal to the n-region, the electrons flow as well as the positive charges flow. Hence the diode is said to be forward biased.
Therefore the correct answer of the above question is option a.

Note: The barrier potential of the depletion region decreases as the charges flow. As a result the energy across the junction decreases. The diffusion of electrons and holes into the depletion layer decreases its width as well as the effective resistance of the junction decreases. In case of the reverse biasing the barrier potential keeps on increasing resulting to decrease or more precisely to stop the flow of current across the diode.