Q123 / 180 · AIIMS 2018 (27 May) · Physics

Assertion : In a common emitter amplifier, the load resistance of the output circuit is 1000 times the resistance of the input circuit. If $\alpha=$ 0.98 , then voltage gain is $49 \times 10^3$. Reason : $\alpha=\frac{\beta}{1-\beta}$ (Symbols have their usual meaning).

A
If both assertion and reason are true and reason is the correct explanation of assertion.
B
If both assertion and reason are true but reason is not the correct explanation of assertion.
Correct answer
C
If assertion is true but reason is false.
D
If both assertion and reason are false.

Solution

Here, $\frac{R_o}{R_i}=1000, \alpha=0.98$ $\beta=\frac{\alpha}{1-\alpha}=\frac{0.98}{1-0.98}=49$ Voltage gain $=\beta \times \frac{R_o}{R_i}=49 \times 1000=49 \times 10^3$

Hence, the correct answer is option: 'C'.

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