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 when the collector current (I_C) is given and the percentage of electrons reaching the collector is known, we can follow these steps:

### Step-by-Step Solution:

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

2. **Convert Percentage to Decimal**:
- The percentage of electrons reaching the collector can be expressed as a decimal (α):
\[ \alpha = \frac{90}{100} = 0.9 \]

3. **Use the Relationship Between Collector Current and Emitter Current**:
- The relationship between the collector current (I_C), emitter current (I_E), and alpha (α) is given by:
\[ \alpha = \frac{I_C}{I_E} \]
- Rearranging this formula to find the emitter current gives:
\[ I_E = \frac{I_C}{\alpha} \]

4. **Substitute the Known Values**:
- Substitute the values of I_C and α into the equation:
\[ I_E = \frac{10 \, \text{mA}}{0.9} \]

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

6. **Final Answer**:
- The emitter current (I_E) is approximately 11.11 mA.

### Final Result:
The emitter current (I_E) is approximately **11.11 mA**.

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