Consider the statements In a semiconductor

(A) There are no free electrons at 0 K.

(B) There are no free electrons at any temperature.

(C) The number of free electrons increases with temperature.

(D) The number of free electrons is less than that in a conductor.

Output of following logic circuit is

The output current versus time curve of a rectifier is shown in the figure. The average value of output current in this case is ........... .

A change of $$0.04 \mathrm{~V}$$ takes place between the base and the emitter when an input signal is connected to the common emitter transistor amplifier. As a result, $$20 ~\mu \mathrm{A}$$ change takes place in the base current and a change of $$2 \mathrm{~mA}$$ takes place in the collector current. The input resistance and AC current gain are