*Question E5A13:
What is an effect of increasing Q in a series resonant circuit?*  

*Correct Answer is  C: Internal voltages increase*  

### AI Response: (may contain errors)  

In a series resonant circuit, the quality factor, or $Q$, is a measure of how "sharp" or selective the resonance is. It is defined as:

$$Q = \frac{X_L}{R} = \frac{X_C}{R}$$

where:
- $X_L$ is the inductive reactance
- $X_C$ is the capacitive reactance
- $R$ is the resistance in the circuit

### Correct Answer: Internal voltages increase

1. **Why the correct answer is correct:**
   - As $Q$ increases, the circuit becomes more selective, meaning it has a narrower bandwidth around its resonant frequency. This increased selectivity results in higher voltages across the reactive components (inductor and capacitor) at resonance. The voltage across these components can be much higher than the applied voltage, due to the energy being stored and exchanged between the inductor and capacitor.

### Why the other choices are incorrect:

2. **Choice A: Fewer components are needed for the same performance**
   - Increasing $Q$ does not reduce the number of components. The number of components is determined by the circuit design and the desired performance characteristics, not by the $Q$ factor.

3. **Choice B: Parasitic effects are minimized**
   - Parasitic effects, such as unwanted resistances, capacitances, and inductances, are not directly minimized by increasing $Q$. In fact, higher $Q$ circuits can be more sensitive to parasitic effects because they rely on precise component values.

4. **Choice D: Phase shift can become uncontrolled**
   - While phase shift is affected by resonance, increasing $Q$ does not make phase shift "uncontrolled." Instead, it makes the phase shift more abrupt around the resonant frequency, but it remains predictable and controlled.

### Useful Formula:

The voltage magnification in a series resonant circuit is given by:

$$V_L = Q \times V_{in}$$

where:
- $V_L$ is the voltage across the inductor (or capacitor) at resonance
- $V_{in}$ is the input voltage

This formula shows how internal voltages increase with higher $Q$.