Basic Electronics - DC Electron Flow

A complete electrical circuit provides a continuous pathway for electrons to flow from the power source, through the circuit, and back to the power source.

By Douglas Krantz

An electrical circuit is a path for electrons to flow. For electrons to flow, they have to go around in a circle (complete circuit). The electrons have to be traveling from the power source (in this case a battery), through a wire, through a load, through another resistor, and finally back into the power source.

Bottom line, there are a limited number of electrons; the circuit has to give back the electrons to power source as the power source provides electrons to the circuit.

Removing a device from the electron path stops the electron flow in the rest of the circuit because the circle is broken.

If the load resistor is removed, the electrons stop in the entire circuit. No electrons are given back, so the power source can't give any more out.

Breaking a wire anywhere in the electrical circuit stops the electrons in the rest of the circuit because the circle is broken.

If a wire is broken or disconnected somewhere besides at the load, the electrons stop in the entire circuit. There is still no electron flow.

It doesn't matter where the electrons are stopped, if they cannot go around the circuit to where they started from, there will be no electron flow.

A complete electrical circuit starts and ends at the power source. In order for electrons to flow, there has to be a complete circuit so that the electrons provided by the power source will be replaced.

Real Life Application

Anytime a circuit has a break in it, whether a switch opens up the circuit, a wire comes loose from a connection, or a wire is just broken, the flow of electrons stops in the entire circuit. The break can be anywhere in the circuit, the electrons stop flowing because the circuit is broken apart.

Having serviced fire alarm systems for nearly 20, Douglas Krantz has compiled his knowledge of the causes of Ground Faults and how to reliably detect them into the book Make It Work - Hunting Ground Faults. The book shows the three types of ground fault, what equipment should be used with each type of ground fault, and how to locate those hard-to-find ground faults.

There's a difference between electron flow and conventional current. See "Which Way Does Electricity Flow?" Unless otherwise stated, electron flow is used here.