|  | 4.1 | Basics of Electricity
| 4.1.8 | Constructing a simple series electrical current
Electrons flow only in circuits that are closed, or complete, loops. The diagram in the main graphic shows a simple circuit, typical of a lantern-style flashlight. The chemical processes in the battery cause charges to be separated, which provides a voltage, or electrical pressure, enabling electrons to flow through various devices. The lines represent a conductor, usually, copper wire. You can think of a switch as two ends of a single wire that can be opened (or broken), and then closed (also known as fixed or shorted), to prevent or to allow, electrons to flow. Finally, the bulb provides resistance to the flow of electrons, causing the electrons to release energy in the form of light. The circuits involved in networking use the same concepts as this very simple circuit, but are much more complex.