Physics Question on Transistors

Question

A change of $8.0 mA$ in the emitter current brings a change of $7.9 mA$ in the collector current. The values of $\alpha$ and $\beta$ are

Answer 1

Solution

Given that, change in emitter current, $\Delta I_{E}=8 mA$
and change in collector current, $\Delta I_{C}=7.9 mA$
We know that,
$\alpha=\frac{\Delta I_{C}}{\Delta I_{E}}$
$\Rightarrow \alpha=\frac{7.9}{8}$
$\Rightarrow \alpha \simeq 0.99$
Also we know that
$\beta =\frac{\alpha}{1-\alpha}$
$\Rightarrow \beta =\frac{\frac{7.9}{8}}{1-\frac{7.9}{8}}$
$=\frac{7.9}{8-7.9}$
or $\beta=\frac{7.9}{0.1}=79$
Hence, the required answer is $\alpha=0.99$ and $\beta=79$