Question

A triode valve has an anode resistance of 20,000 and an amplification factor of 20. The mutual conductance is:

• A. \( 10^{-2} \, \text{mho} \)
• B. \( 10^{-3} \, \text{mho} \)
• C. \( 10^3 \, \text{mho} \)
• D. \( 10^2 \, \text{mho} \)

Hint:

Mutual conductance \( g_m \) is inversely proportional to the anode resistance and directly related to the amplification factor.

Answer 1

The Correct Option is B

To determine the mutual conductance (\( g_m \)) of a triode valve, we need to use the relationship between the amplification factor (\( \mu \)), anode resistance (\( r_a \)), and mutual conductance. The formula is given by:

\( g_m = \frac{\mu}{r_a} \)

Here, we have:

• The amplification factor (\( \mu \)) is 20.
• The anode resistance (\( r_a \)) is 20,000 ohms.

Substituting these values into the formula gives:

\( g_m = \frac{20}{20000} \)

Simplifying the fraction:

\( g_m = \frac{1}{1000} = 10^{-3} \, \text{mho} \)

Thus, the mutual conductance is \( 10^{-3} \, \text{mho} \).

Answer 2

The mutual conductance \( g_m \) is given by the formula: \[ g_m = \frac{\mu}{R_a} \] Where:
- \( \mu \) is the amplification factor,
- \( R_a \) is the anode resistance. Substituting the values: \[ g_m = \frac{20}{20,000} = 10^{-3} \, \text{mho} \]