*Question E7B10:
In Figure E7-1, what is the purpose of R1 and R2?*  

*Correct Answer is  B: Voltage divider bias*  

### AI Response: (may contain errors)  

In the context of the Extra Class exam question E7B10 regarding the purpose of resistors R1 and R2 in a circuit (as depicted in Figure E7-1), let's break down the correct answer and the reasoning behind it.

### Correct Answer: B - Voltage divider bias

1. **Why the correct answer is correct:**
   - R1 and R2 are typically used in a voltage divider configuration to set a stable bias voltage for a transistor. This configuration allows for a consistent operating point, which is crucial for linear amplification. The voltage divider provides a fraction of the supply voltage to the base of the transistor, ensuring it operates in the desired region (active region) for amplification.

2. **Why the other choices are incorrect:**
   - **A: Load resistors**  
     Load resistors are used to limit current or to provide a load for a circuit, but R1 and R2 are not serving this purpose in the context of biasing a transistor.
   
   - **C: Self bias**  
     Self-biasing typically involves using the transistor's own characteristics to set the bias point, often with feedback from the collector to the base. R1 and R2 do not provide this feedback mechanism; instead, they create a fixed bias voltage.
   
   - **D: Feedback**  
     Feedback involves returning a portion of the output signal to the input to stabilize or control the circuit. R1 and R2 do not provide feedback; they simply set a bias voltage.

### Useful Formulas or Rules of Thumb:
- The voltage at the base of the transistor in a voltage divider can be calculated using the formula:
  
  $$V_{B} = V_{CC} \times \frac{R2}{R1 + R2}$$

  where:
  - $V_{B}$ = base voltage
  - $V_{CC}$ = supply voltage
  - $R1$ and $R2$ are the resistances in the voltage divider.

- A common rule of thumb is to choose R1 and R2 such that the base current is much smaller than the current through the divider, ensuring that the biasing is stable and not affected by the transistor's operation.

This explanation should help clarify the role of R1 and R2 in the circuit and prepare you for similar questions on the exam.