To be able to read schematics you must know the schematic symbols. Here is an overview of the most used symbols in circuit diagrams.
Battery
The symbol for a battery is shown below.
A large and a small line is suppose to represent one battery cell so that the image below would suggest a two-cell battery of 3 V. But usually people just draw the battery symbol with one or two cells no matter what voltage it is.
The battery symbol
Capacitor
Capacitors are either polarized or not. The symbols that are used for the two are shown below. Both in European and US style.
A polarized capacitor is marked with a “+” sign. It is important to distinguish between these two because the polarized capacitor needs to be placed correctly according to the “+” sign.
 Standard capacitor (EU style) |  Polarized capacitor (EU style) |
 Standard capacitor (US style) |  Polarized capacitor (US style) |
Resistor
The schematic symbol of the resistor are drawn in two different ways. The american style resistor is drawn as a zigzag resistor while the european style resistor is drawn as a rectangular resistor.
Even though I’m from Europe, I like to draw the zigzag version. I think it is easier to draw and looks better.
 American style resistor |  European style resistor |
Variable resistor (Potentiometer)
The variable resistor or potentiometer is drawn in several different ways. The symbol is often drawn as a resistor with an arrow across it or pointing down on it as the one below.
Variable resistor
Diode
The diode family has several different symbols because there are several different types of diodes. Below is a standard diode, a zener diode and a Light Emitting Diode (LED).
 Standard diode |  Zener diode |
inductor
Light emitting diode (LED)
Schematic Symbols of a Transistor
The most common transistor types are the Bipolar Junction Transistor (BJT) and the Field Effect Transistor (FET). The schematic symbols for these two types are shown below.
 Bipolar Junction Transistor (NPN) |  Field Effect Transistor |
Inductor
The inductor symbol looks like a coiled wire as this is what an inductor essentially is.
Inductor
Integrated Circuit
Integrated circuits (IC) are usually shown as rectangular boxes with pin names. Below, an example of the 555 timer IC is shown.
The “555 timer” integrated circuit
Logic Gates
Here are the schematic representation of the 6 logic gates.
Logic gates
Operational Amplifier
The operational amplifier or “Opamp” is represented as a triangle with two inputs and one output. In some cases, the power supply pins are also added. Below, a version without power supply pins are shown.
Operational amplifier
Switch
A switch can be represented in numerous ways in electronic schematics. Below is one example.
A simple switch
Transformer (Trafo)
The symbol of the transformer looks like two inductors with something in between them.
The transformer symbol
