## Monday, May 28, 2018

### crystal radio step 2

Resonant circuit.

If the link works it is a parallel resonant circuit.
When you space two conductive plates close together but separated by and insulator it forms a capacitor. Place a voltage across a capacitor will put a chatge on its plates.
When you pass current through a wire it creates a magnetic field. Twist the wire into a coil and it will make a stronger field as the field around the loops aid each other.
Put a coil and capacitor in parallel and pulse the circuit with a charge and the coil will send a charge into the capacitor. The capacitor will send energy into the coil. The cycle would repeat forever with perfect components. In the real world we have losses which must be overcome so the peak will decrease with each cycle.
The Q of a coil is the ratio of it reactance to it DC resistance. This is also the gain you can expect to see in a tuned circuit.
To recap a coil stores energy in a magnetic field and a capacitor stores energy in an electric field. Put them in parallel and charge the circuit and it will oscillate. The frequency at which it does is the resonant frequency.
Next post back to the calculator.