When N-P-N transistor is used as an amplifier-

Options

A. the electrons flow from emitter to collector
B. the holes flow from emitter to collector
C. the electrons flow from collector to emitter
D. the holes flow from base to emitter

Answer

To solve the question regarding the operation of an N-P-N transistor when used as an amplifier, let's break it down step by step:

### Step 1: Understand the N-P-N Transistor Structure
An N-P-N transistor consists of three regions:
- **Emitter (N-type)**: Heavily doped with electrons.
- **Base (P-type)**: Thin and lightly doped with holes.
- **Collector (N-type)**: Moderately doped.

### Step 2: Identify the Biasing Conditions
For an N-P-N transistor to function as an amplifier:
- The **emitter-base junction** must be forward-biased.
- The **base-collector junction** must be reverse-biased.

### Step 3: Analyze Charge Carrier Movement
When the transistor is in the forward active region:
- **Electrons** from the emitter move into the base.
- **Holes** from the base move into the emitter.

### Step 4: Determine the Correct Options
Given the options:
1. Electrons flow from emitter to collector.
2. Holes flow from emitter to collector.
3. Electrons flow from collector to emitter.
4. Holes flow from base to emitter.

From our analysis:
- The correct statement regarding the flow of charge carriers in an N-P-N transistor used as an amplifier is that **electrons flow from the emitter to the base**, and **holes flow from the base to the emitter**.

### Conclusion
The correct option is that **electrons flow from emitter to base**, and **holes flow from base to emitter**.

### Final Answer
The electrons flow from the emitter to the base, and the holes flow from the base to the emitter.

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