in a transistor
1. why is the input resistance of a CB configuration low and output resistance high?
2.why is the input resistance of a CE configuration moderately high and output resistance moerately low?
3. why is the input resistance of a CC configuration high and output resistance low?

thank you
Aditya

 

This is a good link for analytical treatment of input and output impedances of transistor configurations.

http://people.deas.harvard.edu/~jones/es15...s/bjt_amps.html

Note that for CE and CC the input impedances are affected by β, thus have high values. You can pretty much observe the configuration where the output impedances affected by β too.