The region in the output voltage versus input voltage graph where a transistor can be used as an amplifier is

In a $CE$ circuit,the collector of a transistor is kept at a constant voltage $V_C = 1.5 \ V$. When the base current changes from $100 \ \mu A$ to $150 \ \mu A$,the collector current changes from $5 \ mA$ to $10 \ mA$. The current gain $\beta$ for this transistor is:

In a $CE$ transistor,when the base current increases by $60 \mu A$,the change in base-emitter voltage is $1.2 \ V$. Then the input resistance is: (in $\Omega$)

In a common emitter amplifier,a.c. current gain is $40$ and input resistance is $2 \ k\Omega$. The load resistance is given as $10 \ k\Omega$. Then the voltage gain is

In a transistor $(\beta=50)$,the voltage across $5 \, k\Omega$ load resistance in the collector circuit is $5 \, V$. The base current is ......... $mA$.

$A$ working transistor with its three legs marked $P, Q$ and $R$ is tested using a multimeter. No conduction is found between $P$ and $Q$. By connecting the common (negative) terminal of the multimeter to $R$ and the other (positive) terminal to $P$ or $Q$,some resistance is seen on the multimeter. Which of the following is true for the transistor?