Electric Circuits

The average person uses a lot of electricity in the many things they do every day. We are used to being able to turn on a light, watch the television, use our mobile devices, and stream music or videos. Because electricity is so much a part of our lives, we should know something about it.

An electrical circuit is like a line or path that the electrical current flows through. The path can be one of two types of circuits:

  • A closed circuit which is joined at each end that creates a loop.
  • An open circuit that lets the electron flow through and then cuts it short because the line is broken. This type of circuit doesn’t let the electrical current continue to flow.

Basic Parts of Electrical Circuits:

To understand the simple electrical circuit you need to know the basic parts and the symbols that the scientists and electricians have given to them.  All of the electronics in use today are based on electronic circuits that combine many parts including wires and components.

  • Conductors: These are materials that allow a path for the flow of electricity. One end of the conductor connects from the cell (power source) to the load. The other end connects the load back to the power source.
  • Switch: This is just a little gap in the conductor that gives you the ability to close or open the circuit. Closing the switch stops the flow of electricity because it closes the circuit.
  • A load: This is the end result of the flow of electricity. Examples of loads are light bulbs which are the final destination of the electrical flow. Loads are also called “resistors.”
  • Cell: This is the power source. When you put more than one cell together they are called a battery.


When scientists, electricians, and engineers want to draw electronic functions they create a diagram known as a schematic. They need to use these pictures because electronic circuits and their many functions can be really detailed.

Schematics show how each of the components are connected to each other, their function, and the ultimate success for the design. To make it easy for professionals around the world to understand schematics, a common set of symbols are used.

electric circuit

What is a Printed Circuit Board?

We use devices every day that have printed circuit boards, including laptops and tablets. These are boards that have many different electronic components in one place to create a working circuit.

The “wires” that we described earlier are all located right into the board and many printed circuit boards have different layers. Each circuit board layer has a specific set of wires and functions.

There are small holes that are drilled into the circuit board called “vias” that connect one layer to another layer. The components are soldered to the surface of the board and it makes electrical connections.

Ground and Power

Printed circuit boards are really complicated and there are usually at least one layer that is devoted to being the “ground” and one layer that is for the “power supply.”

The ground layer is called the ground plane and acts as a return path for the current for many of the components. A majority of the active components that have a minimum of one “pin” that is needed to be connected to ground.

The standard circuit must also have at least one DC power supply. On some of the more complex circuit boards they can have more than one power supply. Remember that “V” represents voltage.

A majority of these power supplies will be +3.3V, +2.5V, or +1.8V. The type of voltage depends on the type of technology that it is being used for. In many cases a full layer of the circuit board is devoted to the main power that is supplying the voltage and is used to keep the power active to the components or parts.

Various electronic components.

Passive Components

There are some components that exist in the current path of the circuit but don’t have a need to be connected to the power supply. These are called “passive components” and examples can include capacitors, connectors, inductors, and resistors.

Active Components

The components that require external power are called “active components.” They connect to the power supply and can inject or push power into the circuit.

Some amplify signals, while other examples can include transistors, diodes, and the CPU (central processing unit) in a computer that has integrated circuits.

Fun Facts about Electronic Circuits

  • The symbol for “printed circuit board” is PCB
  • An analog circuit is a circuit that has a current or voltage that changes constantly with time.
  • Some of the more complex circuits are inside the computer chips in devices we use.
  • Some of the higher end computer CPUs have circuits that are made up of billions of transistors.


What are the two types of electric circuits?
Closed end and Open end

What are the four parts of an electric circuit?
conductors, switch, load, and cell

What are passive components?
components that don’t need to be directly connected to a power supply

What are active components?
components that require external power

What is a printed circuit board?
boards that have many different electronic components in one place to create a working circuit