MHTCET 14 May 2023 Shift 2 Solved Paper

In an n-p-n transistor, the collector current (Ic) is primarily due to the flow of electrons from the emitter to the collector. However, not all the electrons emitted by the emitter reach the collector; a small percentage of them recombine in the base. This percentage is given by the common base current gain (α), which in this case is 80% or 0.80 .
The base current (Ib) can be calculated by knowing that the emitter current (Ie) is the sum of the collector current (Ic) and the base current (Ib). The relationship is given by the equation:
Ie=Ic+Ib
Given that α, which is the common base current gain, is the ratio of the collector current to the emitter current:
α=‌

Ic

Ie

Let's solve for Ie :
Ie=‌

Ic

α

=‌

28‌mA

0.80

=35‌mA
Now, we can find the base current using the initial relation between Ie,Ic, and Ib :
‌Ib=Ie−Ic=35‌mA−28‌mA
‌Ib=7‌mA
Hence, the base current Ib is 7‌mA, which corresponds to Option D.