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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Electric Current through Gases

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

For a 6F6 triode tube, the plate current, plate voltage, and grid...

For a 6F6 triode tube, the plate current, plate voltage, and grid voltage are related by ip=41(Vp+7Vg)1.41i_p = 41(V_p + 7 V_g)^{1.41}, where VpV_p and VgV_g are in volts and ipi_p is in microamperes. If the tube is operated at Vp=250 VV_p = 250 \text{ V} and Vg=−20 VV_g = -20 \text{ V}, calculate the amplification factor.

Options

  1. A3.53.5
  2. B77
  3. C1414
  4. D4141

Correct answer

B. 77

Step-by-step solution

The plate current of a triode is generally expressed as ip=K(Vp+μVg)ni_p = K(V_p + \mu V_g)^n, where μ\mu is the amplification factor.

Comparing the given equation ip=41(Vp+7Vg)1.41i_p = 41(V_p + 7 V_g)^{1.41} with the standard equation, we directly get μ=7\mu = 7.

Alternatively, the amplification factor is defined as μ=−(∂Vp∂Vg)ip\mu = -\left(\dfrac{\partial V_p}{\partial V_g}\right)_{i_p}.

For a constant ipi_p, differentiating the given equation yields:

0=41×1.41(Vp+7Vg)0.41(dVp+7dVg)0 = 41 \times 1.41 (V_p + 7 V_g)^{0.41} (dV_p + 7 dV_g)

dVp+7dVg=0dV_p + 7 dV_g = 0

μ=−dVpdVg=7\mu = -\dfrac{dV_p}{dV_g} = 7
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