*Question G5C02:
What is the output voltage if an input signal is applied to the secondary winding of a 4:1 voltage step-down transformer instead of the primary winding?*  

*Correct Answer is  A: The input voltage is multiplied by 4*  

### AI Response: (may contain errors)  

When dealing with transformers, it's important to understand the relationship between the primary and secondary windings. A transformer with a 4:1 step-down ratio means that if you apply a voltage to the primary winding, the voltage on the secondary winding will be one-fourth of the primary voltage.

However, in this question, the input signal is applied to the secondary winding instead of the primary. This effectively reverses the transformer operation, turning it into a step-up transformer.

1. **Correct Answer Explanation (A):**  
   - When you apply the input voltage to the secondary winding of a 4:1 step-down transformer, it acts as a 1:4 step-up transformer.
   - The voltage is multiplied by the inverse of the step-down ratio, which is 4.
   - Therefore, the output voltage is four times the input voltage.

2. **Incorrect Choices Explanation:**
   - **B: The input voltage is divided by 4**  
     - This would be true if the transformer were used in its intended step-down configuration, with the input applied to the primary. However, since the input is applied to the secondary, the voltage is multiplied, not divided.
   - **C: Additional resistance must be added in series with the primary to prevent overload**  
     - This choice is irrelevant to the voltage transformation process. Adding resistance is not necessary for understanding the voltage change.
   - **D: Additional resistance must be added in parallel with the secondary to prevent overload**  
     - Similar to choice C, this is not related to the voltage transformation. The question is about voltage change, not current handling or overload protection.

3. **Useful Formula:**
   - The voltage transformation ratio for a transformer is given by:
     $$ \frac{V_p}{V_s} = \frac{N_p}{N_s} $$
   - Where $V_p$ and $V_s$ are the primary and secondary voltages, and $N_p$ and $N_s$ are the number of turns in the primary and secondary windings, respectively.
   - In this reversed scenario, the effective turns ratio is inverted, leading to a voltage multiplication by 4.