Simple DC Electrical Circuit – lesson 3

Circuits are defined by the way they are connected: in Series; in Parallel; or a combination of both.

Simple DC circuit

Simplest Circuit

In order to call something a circuit, it must have: a Power Source; a Device to be powered; and wires or conductors to move the electricity from one point to the other.  In addition, that electricity must travel from the power source to the device, and back to that power source.  In other words, it must go in a a circle or complete a circuit.  Without those conditions, it cannot work.

In electrical terminology, we need 3 components:

  1. Source (the Battery)
  2. Path (the wires)
  3. Load (light bulb)

This circuit is complete, but the battery will discharge completely for the light to go off.

So, to make this circuit practical, we need to add a Control or a Switch, to turn it ON or OFF at will.  A two position switch will be either ON (closed circuit) or OFF (open circuit).

Circuit OFF

Circuit OFF

In the drawing to the left, the Switch is turned OFF, of in the Open position.  Electricity from a battery cannot travel through the air, and the circuit is turned OFF.

Can electricity travel through the air? Yes, it can depending on it’s characteristics.  Not too much of a distance (very small gap between two conductors).  Or a very high voltage.  Voltage can be defined as the pressure existing in a circuit.  Compared to the pressure of water in a hose: if you have the very high water pressure from a nozzle, you can water something 20 yards away.  The same goes for electricity.

The Voltage or Pressure from a motorcycle battery is around 12 Volts (not much pressure).  Compare to the voltage in a Spark Plug: 20,000 to 70,000 Volts, and yes, in a Spark Plug, electricity travels between the electrodes, for the purpose of igniting the fuel/air mixture in the combustion chamber of an engine.

Circuit ON

Circuit ON

In this drawing, the circuit is powered and the electricity is flowing through it.  The switch is turned ON or the circuit is Closed.  Electricity flows from the battery, through the wires, the switch, the bulb, then the wire, and it returns back, until the battery gets discharged.

In addition, on motorcycles, to get to the simplest circuit possible, there are two more modifications to be made to this circuit:

  • A circuit protection component or Fuse
  • Use of the Frame and Engine to conduct electricity.

In the next post, I will show the example of the Tail Light circuit on a Honda CB750.

Electricity Lessons Order of Study

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