The amplification factor of a triode is 50. If the grid potential is decreased by 0.20 V, what increase, in plate potential will keep the plate current unchanged ?

Options

A. 5 V
B. 10 V
C. 0.2 V
D. 50 V

Answer

To solve the problem, we need to understand the relationship between the grid potential (Vg), the plate potential (Vp), and the amplification factor (μ) of the triode. The amplification factor is defined as:

\[ \mu = \frac{\Delta V_p}{\Delta V_g} \]

Where:
- \(\Delta V_p\) is the change in plate potential,
- \(\Delta V_g\) is the change in grid potential.

Given:
- The amplification factor \(\mu = 50\),
- The change in grid potential \(\Delta V_g = -0.20 \, V\) (since it is decreased).

We need to find the change in plate potential \(\Delta V_p\) that will keep the plate current unchanged.

### Step-by-Step Solution:

1. **Identify the formula**: We start with the formula for the amplification factor:
\[ \mu = \frac{\Delta V_p}{\Delta V_g} \]

2. **Rearrange the formula**: To find \(\Delta V_p\), we can rearrange the formula:
\[ \Delta V_p = \mu \cdot \Delta V_g \]

3. **Substitute the known values**: Now we substitute the known values into the equation:
\[ \Delta V_p = 50 \cdot (-0.20) \]

4. **Calculate \(\Delta V_p\)**:
\[ \Delta V_p = 50 \cdot (-0.20) = -10 \, V \]

5. **Interpret the result**: The negative sign indicates that the plate potential must increase by 10 V to keep the plate current unchanged when the grid potential is decreased by 0.20 V.

### Final Answer:
The increase in plate potential that will keep the plate current unchanged is \(10 \, V\).

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