*Question E5A04:
What is the magnitude of the impedance of a parallel RLC circuit at resonance?*  

*Correct Answer is  A: Approximately equal to circuit resistance*  

### AI Response: (may contain errors)  

At resonance, a parallel RLC circuit has specific characteristics that determine its impedance. Let's break down why the correct answer is "Approximately equal to circuit resistance" and why the other choices are incorrect.

### Explanation:

1. **Correct Answer: Approximately equal to circuit resistance**

   - At resonance, the inductive reactance ($X_L$) and capacitive reactance ($X_C$) are equal in magnitude but opposite in phase. This means they cancel each other out, leaving only the resistive component to determine the impedance.
   - The impedance ($Z$) of the circuit at resonance is therefore dominated by the resistance ($R$) of the circuit. Thus, the magnitude of the impedance is approximately equal to the circuit resistance.

2. **Why the Other Choices are Incorrect:**

   - **B: Approximately equal to inductive reactance**
     - At resonance, the inductive reactance and capacitive reactance cancel each other out, so the impedance is not determined by either reactance alone.
   
   - **C: Low compared to the circuit resistance**
     - The impedance is not low; it is actually at its maximum at resonance in a parallel RLC circuit, and it is approximately equal to the resistance.
   
   - **D: High compared to the circuit resistance**
     - While the impedance is at its maximum at resonance, it is not higher than the resistance; it is approximately equal to the resistance.

### Useful Formula:

- At resonance in a parallel RLC circuit:
  $$ X_L = X_C $$
  - This means the reactive components cancel out, leaving the impedance to be determined by the resistance.

Understanding these principles will help you correctly identify the behavior of a parallel RLC circuit at resonance.