why short cuit the output when finding gain?

[jason]

Hi All


May I know the reason why sometimes we need to short circuit the output
in order to find the curent gain or voltage gain of a circuit?
Why do we need a short circuit current gain?

Usually we wish to know the voltage gain or current gain of a circuit?
Why?
Just a stupid question, is it true that when we are interesting in
current gain for a circuit, that implies voltage gain is almost
negligible?

Kindly enligthen

rgds and thanks
jason