SOLUTION

Applying external d.c. voltage to an electronic device is called biasing. Depending upon the polarity of the d.c. voltage externally applied to it, the biasing is classified as forward biasing and reverse biasing. 

Forward Biasing of P-N Junction Diode

If an external d.c. voltage is connected in such a way that the p-region terminal is connected to the positive of the D.C voltage and the n-region is connected to the negative of the d.c. voltage, the biasing condition is called forward bias. The p-n junction is said to be forward-biased.

Reverse Biasing of P-N Junction Diode

If an external d.c. voltage is connected in such a way that the p-region terminal of a p-n junction is connected to the negative of the battery and the n-region terminal of a p-n junction is connected to the positive terminal of the battery, the biasing condition is called reverse biasing of a PN junction.