If ${l_1}, {l_2}, {l_3}$ are the lengths of the emitter,base,and collector of a transistor,respectively,then:

Given below are two statements:
Statement $I:$ In a typical transistor,all three regions emitter,base and collector have same doping level.
Statement $II:$ In a transistor,collector is the thickest and base is the thinnest segment.
In the light of the above statements,choose the most appropriate answer from the options given below.

For a transistor to be used as an amplifier,which of the following conditions must be satisfied?

In the $CB$ mode of a transistor, when the collector voltage changes by $0.5 \ V$, the collector current changes by $0.05 \ mA$. What is the output resistance in $k\Omega$?

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:

$A$ $NPN$ transistor conducts when