Explain , why the input resistance of a transistor is low and output resistance is high.

Explanation

When a p-n junction is forward biased width of the depletion layer decreasea and there is large change in current even for a small change in potential. Hence, it offers small resistance. However, when a p-n junction is reverse biased, width of the depletion layer increases and there is very small change in current for a large change in potential. Hence, we can say that it offers high resistance.