The most useful electronic schematic symbols

These schematic symbols were created using ProSchematic a super easy to use schematic drawing tool (schematic capture tool).

Note: Passive devices are devices that do not change or amplify voltage or current when another parameter is altered i.e. they react the same way and when a voltage or current (ac or dc) is applied a constant output is observed e.g. a resistor, capacitor, inductior, diode.

Note: Active devices are the opposite of passive i.e. they alter their behaviour due to another parameter usualy to amplify (e.g. transistor) but also act as a controlled switch (e.g. thyristor). Another example is the resistance of a fet changing when the gate voltage changes.

Schematic symbols for passive devices:

Resistors

Thermistor

or temperature dependent resistor

Presets

Those three pin skeleton things that never fit into veroboard and you end up soldering veropins and piggybacking the thing on top!
Really the same as a variable resistor with no case and much smaller.

Variable resistors

Proper panel mount units with a metal or plastic spindle - plastic is easier to cut.

Light dependent resistor

Capacitors

Electrolytic capacitors

These contain a electrolyte solution and when placed the wrong way round generally explode. These are also the symbols for tantalum which when placed the wrong way round generally smoke!

Variable capacitors

These are the ones on a transistor radio 265pF (or larger for older radios).

Preset or trimmer capacitors

These are miniature capacitors either with overlapping vanes (small round) ~65pF or a single plate that is rasied of the other with a screw.