Understanding Resonance in Series RLC Circuits

In a series RLC circuit driven by an AC signal generator, what causes the current to undergo resonance?

• A. Voltage amplitude
• B. Supply frequency
• C. Capacitance value
• D. Inductance value

Answer: (B)

The phenomenon of resonance in a series RLC circuit is fundamentally linked to the supply frequency. When the frequency of the AC signal from the generator matches the natural frequency of the RLC circuit, resonance occurs. At this point, the inductive and capacitive reactances cancel each other out, resulting in a condition where the impedance of the circuit is minimized to just the resistance (R). This means that the circuit can draw maximum current from the voltage source. The frequency at which this occurs is determined by the values of the inductance (L) and capacitance (C) in the circuit, specifically calculated by the formula \( f_0 = \frac{1}{2\pi\sqrt{LC}} \). Thus, when the supply frequency aligns with this natural frequency, resonance is achieved, leading to a significant increase in current flow in the circuit. While the values of capacitance and inductance also play a role in determining the resonant frequency, it is ultimately the supply frequency that triggers the actual resonance phenomenon by matching this calculated frequency. Therefore, the supply frequency is crucial in causing resonance in a series RLC circuit.

When tackling the intricacies of series RLC circuits, one of the standout features that pop up is resonance. But what exactly makes current undergo this phenomenon? Well, you’ve stumbled onto a topic that’s not just pivotal in electrical engineering but also a fantastic little corner of physics.

So, let’s start with the fundamentals of resonance. In a series RLC circuit, we have resistors, inductors, and capacitors all working together. The magic happens when an AC signal generator sends out electrical signals. If the frequency of this generator aligns perfectly with the circuit's natural frequency, the conditions for resonance are met. You see, it’s all about synchronization!

Now, let’s break it down. The correct answer to our burning question about what specifically causes the current to resonate is the supply frequency. When this frequency hits just right—matching the resonance frequency calculated using ( f_0 = \frac{1}{2\pi\sqrt{LC}} )—wonderful things happen. The inductive reactance from the inductor and the capacitive reactance from the capacitor negate each other. Imagine a perfectly choreographed dance where one partner leads and the other follows flawlessly. At this exact moment, the impedance of the circuit drops to an exhilarating level—just the resistance (R).

At resonance, the circuit can draw maximum current from the voltage source, which sounds like the party you don’t want to miss! But what’s exciting here is how the supply frequency serves as the key to this orchestration. While you might think that capacitance or inductance values could wrestle the spotlight, they are more like the supporting cast. Sure, they help determine your resonant frequency, but it’s the supply frequency that truly ignites the magic.

Here’s the thing—engineering students often wrestle with these concepts, and it’s natural to feel overwhelmed. Just remember: resonance is about balance, like life itself! A little bit of inductance here, a sprinkle of capacitance there, and when the generator sets the right tone with its frequency, everything aligns.

Let’s not step away from why this matters. Understanding resonance isn’t just an academic exercise. It’s crucial in many applications, from signal processing to communication systems. Getting to grips with these concepts makes you more than just a student; it primes you for the world of an engineer, where theory meets real-world challenges.

In summary, as you prepare for the Electronics Engineering board exams, remember that when discussing resonance in RLC circuits, the supply frequency is the main character that drives the narrative. Everything else—inductance and capacitance—is there to enhance the drama. Keep that in mind as you study, and you’ll be resonating with success before you know it!