Question

If an emitter current is changed by $4mA$, the collector current changes by $3.5mA$. The value of $\beta$ will be:

• A. $7$
• B. $0.875$
• C. $0.5$
• D. $3.5$

Answer 1

The correct option is A

$7$

Step 1: Given data:

An emitter current is changed by $∆I_E=4mA$

The collector current changes by $∆I_c=3.5mA$

Step 2: Formula used:

Knowing the formula,

Current gain, $\alpha =\frac{∆I_c}{∆I_E}$

Now substitute the value in this formula,

$$\begin{gathered} \alpha =\frac{3.5}{4} \\ \alpha =\frac{7}{8} \end{gathered}$$

Also, current gain, $\beta =\frac{\alpha }{1-\alpha }$

Now substitute the value in this formula,

$$\begin{gathered} \beta =\frac{{\displaystyle \frac{7}{8}}}{1-{\displaystyle \frac{7}{8}}} \\ \beta =\frac{{\displaystyle 7}}{1} \\ \beta =7 \end{gathered}$$

Therefore the value of $\beta$is $7$.

Hence, the correct option is (A).