In a silicon transistor, a change of `7.89 mA` in the emitter current produce a change of 7.8 mA in the collector current. What change in the base current is necessary to produce an equivalent change in the collector current?

Options

A. 7.8 mA
B. 7.89 mA
C. 0.09 mA
D. zero

Answer

To solve the problem, we need to understand the relationship between the emitter current (IE), collector current (IC), and base current (IB) in a transistor. The relationship is given by the equation:

\[ I_E = I_B + I_C \]

Where:
- \( I_E \) = Emitter current
- \( I_B \) = Base current
- \( I_C \) = Collector current

### Step-by-Step Solution:

1. **Identify the given values:**
- Change in emitter current, \( \Delta I_E = 7.89 \, \text{mA} \)
- Change in collector current, \( \Delta I_C = 7.8 \, \text{mA} \)

2. **Use the relationship between the currents:**
- From the equation \( I_E = I_B + I_C \), we can express the change in emitter current in terms of the changes in base and collector currents:
\[ \Delta I_E = \Delta I_B + \Delta I_C \]

3. **Substitute the known values:**
- Rearranging the equation gives us:
\[ \Delta I_B = \Delta I_E - \Delta I_C \]
- Substitute the values:
\[ \Delta I_B = 7.89 \, \text{mA} - 7.8 \, \text{mA} \]

4. **Calculate the change in base current:**
\[ \Delta I_B = 0.09 \, \text{mA} \]

5. **Conclusion:**
- The change in the base current necessary to produce an equivalent change in the collector current is \( 0.09 \, \text{mA} \).

### Final Answer:
The change in the base current necessary to produce an equivalent change in the collector current is **0.09 mA**.