Introduction to Electricity

basic electrical circuit

Basic complete electrical circuit

We all use electricity every day. From the moment our electric clock wakes us up in the morning until we turn the light off for bed at night. It has become so common place, that we take it for granted. I am going to discuss the various parts of an electrical circuit and what happens when you have all the pieces connected correctly.

Main Properties of Electricity

  • pressure (voltage)
  • current (amps)
  • resistance (ohms)

Electricity begins in atoms.  These are the tiny microscopic building blocks that make up everything. We will talk about atoms in another article, but for now just bear with me.  Atoms are made up of protrons, neutrons and electrons.  It is the electrons that we are most interested in.  The process of atoms moving their electrons in a path (or circuit) is electrical current.

Voltage is the force that makes these electrons jump from atom to atom.  In a typical DC (Direct Current) circuit such as a flashlight, the voltage is created by the battery.  In the diagram, you see there is a battery which is connected to a light bulb.  The voltage from the battery is stimulating the electrons in the circuit to give up electrons.  The electrons are moving from the negative side of the battery (the black line shown with a minus “-” sign). When the electrons reach the light bulb, it converts these extra electrons to light and then passes them back to the battery through the positive line (the red line shown with a “+” sign).

Resistance slows down the flow of electrons.  We get some resistance just from the wires coming out of the battery. The smaller the wires the greater the resistance.  The main source of resistance in our example is the light bulb itself. The filament causes the flowing electrons to enter a smaller space.

Short Circuit

If we took the light bulb out of our example and connected the negative and positive wires together we would get a short circuit. The electrons would move quickly from the negative to the positive side of the battery discharging it quickly.

Competed Circuit

basic electricity incomplete circuit

Basic open electrical circuit

An electrical circuit must be complete meaning that there needs to be a direct connection from both sides of the power source. If that line is severed, the circuit will not be complete and electrons will not flow. This law is why we can have switches. Think of turning on the light in your bedroom. When you flip the switch to the on position, it is completing the circuit and allowing the electrons to flow to your light.

Notice in the diagram that the negative connection was removed from the light bulb. This caused the bulb to stop shining because the electrons are no longer flowing from the battery.

This happens because unlike water electrons don’t really flow, the are attracted by atoms that are missing electrons. This is where the positive connection comes in.  The positive side of the battery is in need of elections and the negative side of the battery has extra electrons. The positive side pulls the electrons from the negative side.  Have you ever charged a dead car battery (or seen it done)? If the negative side of the jumper cables are attached and the the positive side, you usually see a spark or arch.  This is caused by the positive side of the circuit pulling so hard for electrons from the negative side that the electrons literally jump through the air to get to the other side.


We talked about voltage as the pressure moving electricity, current (amps) as the flow of electrons, and resistance (ohms) as the slowing of electrons in the circuit.  I also explained that a circuit needs to be complete because the positive side is pulling electrons from the negative side.


Take 2 pieces of coper wire and attach them to both sides of a flash light light bulb.  Attach the other ends of the wire to both ends of a C or D battery.  See if the light bulb lights up?

Post your results in the comments!

Extra Credit

What happens if you add more batteries? Make sure you connect the positive side of each battery to the negative side of the next.

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One Response to “Introduction to Electricity”

  1. […] a switch. If you don’t have a basic understanding of electricity, take a minute to read my Introduction to Electricity post. Don’t worry, we will […]

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