In an n-p-n transistor, the collector current is 10 mA. If 90% of the electrons emitted reach the collector, then the emitter current will be

Options

A. 9mA
B. 11mA
C. 1 mA
D. 0.1 mA

Answer

To find the emitter current (I_E) in an n-p-n transistor given the collector current (I_C) and the percentage of electrons reaching the collector, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Collector current, I_C = 10 mA
- Percentage of electrons reaching the collector = 90%

2. **Convert Percentage to Decimal:**
- The fraction of electrons reaching the collector can be expressed as:
\[ \frac{I_C}{I_E} = 0.9 \]

3. **Relate Collector Current to Emitter Current:**
- From the relationship established in step 2, we can express I_C in terms of I_E:
\[ I_C = 0.9 \cdot I_E \]

4. **Rearrange the Equation to Solve for Emitter Current:**
- To find I_E, rearrange the equation:
\[ I_E = \frac{I_C}{0.9} \]

5. **Substitute the Known Value of Collector Current:**
- Substitute I_C = 10 mA into the equation:
\[ I_E = \frac{10 \text{ mA}}{0.9} \]

6. **Calculate Emitter Current:**
- Perform the calculation:
\[ I_E = \frac{10}{0.9} \approx 11.11 \text{ mA} \]

7. **Round to Appropriate Significant Figures:**
- Since we are dealing with current in mA, we can round it to:
\[ I_E \approx 11 \text{ mA} \]

8. **Conclusion:**
- The emitter current (I_E) is approximately 11 mA.

### Final Answer:
The emitter current (I_E) is **11 mA**.

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