The resultant voltage gain in a series combination of two or more amplifiers is .......

The device that can act as a complete electronic circuit is

$Ge$ and $Si$ diodes conduct at $0.3 \, V$ and $0.7 \, V$ respectively. In the following figure,if the $Ge$ diode connection is reversed,the value of $V_0$ changes by how many volts?

The negative feedback in an amplifier

Arvind needs to identify the electrical components from a group of components labelled as $A, B, C$ and $D$. He performed some simple tests and obtained the following observations:
$(a)$ $A$ has a silver ring at one end,with two terminals. It conducts electricity only in one direction.
$(b)$ $B$ is connected to a $D.C.$ source,but the current gradually decreases and becomes zero. It is a two-terminal device and behaves the same in both directions.
$(c)$ $C$ is a two-terminal device,which conducts electricity only in one direction,while emitting light.
$(d)$ $D$ is a two-terminal device with several coloured rings on it. It conducts current in both directions with the same steady current.
The correct identification of $A, B, C$ and $D$ are respectively:

Two amplifiers are connected one after the other in series (cascade). The first amplifier has a voltage gain of $10$ and the second has a voltage gain of $20$. If the input signal is $0.01\, V$,the output $ac$ signal will be........$V$.