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Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectric Current through Gases

When the load resistance of an amplifier is modified from 4 k to 8 k , its gain factor increases from 10 to 12 . Determine the plate resistance.

Options

  1. A6 k
  2. B4 k
  3. C8 k
  4. D2 k

Correct answer

D. 2 k

Step-by-step solution

The voltage gain of an amplifier is given by A = R_L R_p + R_L where is the amplification factor, R_p is the plate resistance, and R_L is the load resistance. For the first case: 10 = 4 R_p + 4 For the second case: 12 = 8 R_p + 8 Dividing the first equation by the second equation: 10 12 = 4(R_p + 8) 8(R_p + 4) 5 6 = R_p + 8 2(R_p + 4) 10(R_p + 4) = 6(R_p + 8) 10R_p + 40 = 6R_p + 48 4R_p = 8 R_p = 2 k

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