LC Resonance Calculator
Calculate resonant frequency and visualize response.
What is LC Resonance?
An LC Circuit (or "Tank Circuit") is the electronic equivalent of a pendulum. It consists of an Inductor (L) and a Capacitor (C) connected together. At a specific magic frequency called the Resonant Frequency, energy flows back and forth between the inductor's magnetic field and the capacitor's electric field with almost zero effort.
This phenomenon allows the circuit to selectively amplify one specific frequency while rejecting all others. This is the heart of every radio receiver: when you "tune" a radio, you are physically changing the C or L value to move this resonance point.
The Resonance Formula
The resonant frequency (f₀) is the point where the Inductive Reactance (XL) exactly cancels out the Capacitive Reactance (XC).
f₀ = 1 / (2π√[LC])
To use this formula:
- L: Inductance in Henries (H)
- C: Capacitance in Farads (F)
- f₀: Frequency in Hertz (Hz)
Reactance Cancellation
At resonance:
XL = 2πfL
XC = 1 / (2πfC)
XTotal = XL - XC = 0Ω (in a series circuit)
Practical Applications
- Radio Tuners: Selecting the 101.5 MHz carrier wave from the air while ignoring 98.5 MHz.
- NFC / RFID Tags: Your credit card is powered by an LC coil tuned to 13.56 MHz, capturing energy from the payment terminal.
- Induction Heating: Using high-current resonance to melt metal by inducing eddy currents.
FAQ
What is the "Q Factor"?
Quality Factor (Q) measures how "pure" the resonance is. A high Q means a very sharp, narrow peak (good for selecting one radio station). A low Q means a wide, flat bandwidth. Q is determined by resistance; less resistance = Higher Q.
Series vs Parallel Resonance?
They are opposites! In a Series LC circuit, impedance drops to near zero at resonance (short circuit). In a Parallel LC circuit, impedance becomes infinite at resonance (open circuit). Both are useful.
Why do I need a variable capacitor?
Since Inductors are hard to change mechanically, most tuning circuits use a variable capacitor (varicap or air-variable) to adjust the C value, which shifts the resonant frequency f₀ up or down.