Theory and troubleshooting using short modules packed with images to make learning quick and easy.
In a DC (direct current) circuit, all the electrons hop from electron to electron in a single direction, hence the name, direct current. Since electrons only flow in one direction, electrical polarity matters, so you’ll need to place each wire exactly how it’s depicted on a wiring diagram.
Polarity is the direction of current flow in a circuit from the two poles, positive and negative. You require two points of differential charge for any electron movement to take place.
In an AC circuit, each pole alternates between positive and negative 60 times per second. You can see from the image of the AC sine wave, that the change in polarity of AC does not happen instantly, although close to and 60 times per second (Hertz).
A most basic electrical circuit will have three components
While not entirely needed, most circuits will include a switch. A switch will stop the flow of electricity through the conductor to the load.
As you can see, with an open switch, power cannot get past the switch to turn on the lights.
With the switch in the closed position, power is allowed to flow through the circuit and turn the lights on.
Earlier we covered electrons moving from atom to atom. Metallic bonding forms copper. The bond is made when many metal atoms share their collected valence electrons. The valence electrons are not attached to any specific atom, so they move around freely.
Now to get these electrons moving in one direction and being of more use, they just need a push. This is by applying an electromotive force (emf), also known as voltage.
Sticking with the water analogies, amperes, or amps for short, is the amount of water flowing through the hose. The higher the pressure (voltage), the more water flows (amps) out of the hose. In Ohm’s Law, amperage is represented by “I.”
Almost all material has some form of resistance to electrical flow. Without resistance, you’d have no way for a circuit to do useful work. Like stated earlier, conductors are materials that allow current to flow, and insulators don’t. Conductors have little resistance.
Resistance in a circuit is measured in Ohms or the Greek letter “Ω.” Current flowing through an electric range or toaster causes the elements to generate heat to cook your food by using resistance. In Ohm’s Law, resistance is represented by “R.”
To quickly sum up voltage, current, and resistance.
Voltage is the driving pressure which is the high and low potential in the water tower below.
Current (amperes or amps) is the resulting flow which is the water flowing through the pipe in the water tower below.
Resistance completes useful work. The wheel spinning in the water tower below.
series
noun
So given the above definition, a series circuit is when there’s only a single path for current to flow. Any break in the wiring or a faulty load will stop current throughout the entire series circuit.
A load is anything in the circuit that does useful work, like the lightbulb in the example below. The inexpensive and/or old Christmas lights have this downfall. When a single bulb burns out, the entire string of lights goes out.
A parallel circuit allows for more than one path for current to flow. We have the same two loads from the series circuit below, but we have two paths now for electrons to flow. Each pathway for current to flow is called a branch.
2 loads in series Vs. 2 loads in a parallel circuit
In a parallel circuit, if the light (load) in branch 1 were to be faulty, the light (load) in branch two would still function as there’s another pathway around the faulty load to take for the electrons to flow.
So let’s quickly recap the representations for voltage, resistance, and amperage in the Ohm’s Law triangle:
E = Voltage (electromagnetic force)
I = Current (amps)
R = Resistance
For a given resistance, the current is directly proportional to voltage. That said, if you increase the voltage in a circuit with a fixed resistance, the current will increase. If you decrease the voltage in a circuit with a fixed resistance, the current will decrease.