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Electrical extras: parallel resistors, LC resonance & EM spectrum

modified2026-07-21statusfinished

Three more electronics solvers: parallel resistor networks, LC resonant circuits, and the electromagnetic spectrum relation between frequency, wavelength, and photon energy.

Index

Multi-resistor parallel network solver

Governing equations

$$\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \cdots + \frac{1}{R_n}$$

Equivalent resistance of resistors in parallel; current divider follows $I_k = I_{total} \cdot R_{eq}/R_k$. Source: standard circuit theory.

R1 R2 R3
FIG. 01 — resistors R1, R2, R3, ... connected in parallel across the same node pair
Equivalent resistance R_eq

LC circuit resonant frequency & impedance

Governing equations

$$f_0 = \frac{1}{2\pi\sqrt{LC}}, \quad Z_L = 2\pi f_0 L = \frac{1}{2\pi f_0 C}$$

Resonant frequency of a series/parallel LC tank circuit, where inductive and capacitive reactance cancel. Source: standard circuit theory.

L C
FIG. 02 — parallel LC tank: inductor L and capacitor C across the same nodes
Resonant frequency f₀
Characteristic impedance Z

Electromagnetic frequency, wavelength & photon energy

Governing equations

$$c = f\lambda, \quad E = hf = \frac{hc}{\lambda}$$

Relation between frequency, wavelength, and photon energy for electromagnetic radiation. $c=2.998\times10^8$ m/s, $h=6.626\times10^{-34}$ J·s. Source: standard EM/quantum physics.

λ (wavelength)
FIG. 03 — one wavelength λ of an electromagnetic wave
Frequency
Wavelength
Photon energy