Find the value of current $I$ in the following circuits.

The box in the circuit below has two inputs marked $V_{+}$ and $V_{-}$ and a single output marked $V_{o}$. The output obeys the following relation:
$V_{o} = \begin{cases} +10 \, V & \text{if } V_{+} > V_{-} \\ -10 \, V & \text{if } V_{+} < V_{-} \end{cases}$
Which of the following graphs represents the output $V_{o}$ as a function of time $t$?

In an oscillator,if $\beta$ is the feedback factor and $A$ is the gain of the amplifier,then sustained oscillations are obtained when:

Which of the following components acts as a complete electronic circuit?

$A$ $p-n$ junction diode cannot be used

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........$V$.