Electronics 01
LC Resonant Frequency Formula: Derivation, Q and Real Parts
f = 1/(2π√LC), derived from energy sloshing, with Q, bandwidth, an AM tuner worked example, and why real coils and capacitors miss the ideal number.
inductors
Electronics 02
Relay Flyback Diode: Why You Need One and Which to Use
A relay coil can kick back 1,000 V at turn-off. A flyback diode stops it but slows contact release about 5x. Here is the math and the diode plus zener fix.