Question

In a ${{PN}}$ junction:
A) High potential at ${{N}}$ side and low potential at ${{P}}$ side
B) High potential at ${{P}}$ side and low potential at ${{N}}$ side
C) ${{P}}$ and ${{N}}$ both are at the same potential
D) Undetermined

Answer 1

Hint: In a ${{PN}}$ junction, the ${{P}}$ side (positive side) has an excess of holes and the ${{N}}$ side (negative side) has an excess of electrons, therefore the electrons from the ${{N}}$ side travel to the interface while the holes from the ${{P}}$ side also travel to the interface leaving a positive charge in ${{N}}$ side and negative side in ${{P}}$ side.

Complete solution:
A ${{PN}}$ junction is a type of semiconductor. It is an interface at which the ${{P}}$ type silicon and ${{N}}$ type silicon have contact with each other. The ${{P}}$ side contains an excess of electrons or deficiency of electrons and is positively charged while the ${{N}}$ side has an excess of electrons and is negatively charged. The ${{P}}$ side can be considered as an anode while the ${{N}}$ side can be considered as a cathode. The electrons from the ${{N}}$ side come to the interface and the holes from ${{P}}$ side also travel to the interface; this interface is known as the depletion region. This leaves behind the ${{N}}$ side positively charged and the ${{P}}$ side as negatively charged. Therefore, the current flows from${{N}}$ side to the ${{P}}$ side. As we know that current flows from the area of higher potential to the area of lower potential therefore ${{N}}$ side is at higher potential while ${{P}}$ side is at lower potential.

Note: Although there is no battery connected to the system, then even there will be a flow of current because of the flow of electrons that took place in the diode to fill up the holes which created a net positive charge in the ${{N}}$ side and a negative charge in the ${{P}}$ side.