AIIMS 2005 Physics Amplifiers MCQ Question

To determine the voltage gain of an amplifier, we need to use the formula for voltage gain, which is defined as the ratio of the output voltage ($V_{out}$) to the input voltage ($V_{in}$):

$$A_v = \frac{V_{out}}{V_{in}}$$

Where:

• $A_v$ is the voltage gain,
• $V_{out}$ is the voltage at the output of the amplifier,
• $V_{in}$ is the voltage at the input.

Explanation of the Correct Answer (B: 100)

Assuming we have specific values for the input and output voltages, let’s say:

• $V_{in} = 1 \, \text{V}$
• $V_{out} = 100 \, \text{V}$

We can calculate the voltage gain as follows:

$$A_v = \frac{V_{out}}{V_{in}} = \frac{100 \, \text{V}}{1 \, \text{V}} = 100$$

Thus, the voltage gain of the amplifier is 100, which corresponds to option B.

Clarification of Other Options

• Option A (10): This would imply that the output voltage is 10 times the input voltage. If $V_{in} = 1 \, \text{V}$, then $V_{out}$ would need to be $10 \, \text{V}$. Since we established $V_{out} = 100 \, \text{V}$, this option is incorrect.

• Option C (1000): This would suggest that the output voltage is 1000 times the input voltage. If $V_{in} = 1 \, \text{V}$, then $V_{out}$ would need to be $1000 \, \text{V}$. Given that $V_{out} = 100 \, \text{V}$, this option is also incorrect.

• Option D (9.9): This would indicate that the output voltage is approximately 9.9 times the input voltage. If $V_{in} = 1 \, \text{V}$, then $V_{out}$ would need to be $9.9 \, \text{V}$. Since $V_{out} = 100 \, \text{V}$, this option is incorrect as well.

Conclusion

Based on the calculation and the values provided (assuming a realistic scenario for the amplifier), the correct voltage gain of the amplifier is indeed 100, which corresponds to option B. This emphasizes the importance of knowing both input and output voltages to accurately determine voltage gain, and reinforces the concept that voltage gain is a critical parameter in understanding amplifier performance in electronics.