This application contains descriptions and pictures of electrical symbols. You can search for symbols, display info and zoom the symbol's picture. The symbols can be exported to use in external programs. The destination directory is Documents/ElectricalSymbolsForElectronics. The app is without ads.
More info: ecstudiosystems.com/symbols/

Supported symbols:

Wire
Connected Wires
Not Connected Wires
Earth Ground
Chassis Ground
Signal Ground
Voltage Source
Current Source
AC Voltage Source
Generator
Battery Cell
Battery
Controlled Voltage Source
Controlled Current Source
Resistor (IEEE)
Resistor (IEC)
Potentiometer (IEEE)
Potentiometer (IEC)
Rheostat (IEEE)
Rheostat (IEC)
Trimmer
Thermistor
Photoresistor
Capacitor
Polarized Capacitor
Variable Capacitor
Inductor
Iron Core Inductor
Variable Inductor
Diode
Zener Diode
Schottky Diode
Varicap
Tunnel Diode
Light Emitting Diode (LED)
Photodiode
NPN Bipolar Transistor
PNP Bipolar Transistor
NPN Darlington
PNP Darlington
JFET-N Transistor
JFET-P Transistor
MOSFET-N Depletion Mode Transistor
MOSFET-P Depletion Mode Transistor
MOSFET-N Enhancement Mode Transistor
MOSFET-P Enhancement Mode Transistor
NOT Gate (Inverter)
AND Gate
NAND Gate
OR Gate
NOR Gate
XOR Gate
XNOR Gate
D Flip-Flop
Multiplexer / Mux 2 to 1
Multiplexer / Mux 4 to 1
Demultiplexer / Demux 1 to 4
Voltmeter
Ammeter
Ohmmeter
Wattmeter
Lamp
Light Bulb
Neon Lamp
Switch SPST
Switch SPDT
Pushbutton (N.O)
Pushbutton (N.C)
Jumper
Relay SPST
Relay SPDT
Antenna
Dipole Antenna
Loop Antenna (IEC)
Loop Antenna (IEEE)
Motor
Transformer
Fuse
Bus
Optocoupler
Operational Amplifier
Schmitt Trigger
Analog-to-Digital Converter
Digital-to-Analog Converter
Crystal Oscillator
Microphone (IEC)
Microphone (IEEE)
Buzzer
Loudspeaker