EFA:Basic Components

Let’s take a look at some common components that you will need to use when you start building your circuits.


Conductors are materials that allow electrical current to flow. Different materials have different levels of conductivity. Metals are really good conductors and have only very little resistance. Electric wires are usually made of copper, which is an excellent conductor.


Insulators are materials that do not conduct electricity, or more accurately, they are materials that make it really really hard for electricity to flow. Commonly used insulators are plastics and ceramics. The plastic around an electric wire is an insulator.

Power Supply

Whenever we are doing something with electronics, we are obviously going to need some sort of source of electric power. It could be a battery, a power supply, or the USB port of your computer. In our case, the power will usually come from either a 9V power supply or from the Arduino.

These are common symbols for different power sources that you will see in schematics and circuit diagrams.

pow1 pow2 pow3


As the name would suggest, resistors resist the flow of current. They come in different values and power ratings. You will usually run into resistors that will have either 4 or 5 colored bands that tell the values of a resistor.


There are two common symbols for resistors in schematics and circuit diagrams. The zig-zag line is used in the US and the rectangle more in Europe. I personally prefer to use the squiggly zig-zag.



Capacitors are like tiny batteries that can store electrical energy. The unit for capacitance is farad (F). One farad is fairly large amount so most components you see will be in the micro-, nano-, or picofarad scale.

Some capacitors (electrolytic capacitors) have polarity. The negative side is marked with a line on the part itself. Always make sure you plug them the correct way or it might blow up.



Diodes & LEDs (Light Emitting Diodes)

Diodes are components that allow the current to flow only one direction. LEDs are also diodes that emit light when current flows through them.





Variable Resistors (LDR, Potentiometer…)


*all schematic images on this page are from this Sparkfun tutorial. (CC BY-SA 4.0)