The equation for an LCR circuit (which includes an inductor, a capacitor, and a resistor in series or parallel) depends on whether it's a series or parallel configuration. I'll give you the general form for both types.
1. Series LCR Circuit:
In a series LCR circuit, the resistor (R), inductor (L), and capacitor (C) are connected in a single path. The governing equation is derived from Kirchhoff's Voltage Law (KVL).
The differential equation for a series LCR circuit is:
\[
L \frac{d^2 q}{dt^2} + R \frac{dq}{dt} + \frac{q}{C} = 0
\]
Where:
- \( q(t) \) is the charge on the capacitor at time \( t \).
- \( L \) is the inductance.
- \( R \) is the resistance.
- \( C \) is the capacitance.
Alternatively, you can express the equation in terms of the voltage across the components. The total voltage across the circuit is:
\[
V(t) = L \frac{di}{dt} + Ri + \frac{1}{C} \int i \, dt
\]
Where:
- \( i(t) \) is the current in the circuit.
- \( V(t) \) is the applied voltage.
2. Parallel LCR Circuit:
In a parallel LCR circuit, the inductor, capacitor, and resistor are connected in parallel, and the governing equation is:
\[
\frac{1}{L} \frac{d^2 q}{dt^2} + \frac{1}{R} \frac{dq}{dt} + \frac{1}{C} q = 0
\]
Where the terms are similar as before, and \( q(t) \) is the charge on the capacitor.
Natural Frequency and Damping:
For both types of circuits, the behavior of the circuit is often analyzed in terms of the
resonant frequency \( \omega_0 \) and the
damping factor \( \zeta \).
\[
\omega_0 = \frac{1}{\sqrt{LC}}
\]
\[
\zeta = \frac{R}{2} \sqrt{\frac{C}{L}}
\]
These help in understanding whether the circuit is underdamped, critically damped, or overdamped, which describes how the circuit responds to oscillations.
Let me know if you need further details on how to solve these equations or analyze the circuit behavior!