An electrical connection between discrete points allows the flow of electrons, (current). A pair of connections is needed for a circuit.

Between points with a low voltage difference between them, direct current flow can be controlled by a switch. However, if the points are not connected, and the voltage difference between those points is high enough, electrical ionization of the atmosphere will occur, and current flow will tend to occur along the path of least resistance.

• For example, in one high-voltage (60 kV) RADAR laboratory, an individual (who fortunately survived this) pointed his finger at an electrical component: "What's that?". Fortunately, his elbow was crooked, as direct current flow occurred from the high voltage component, arcing through the air to his finger, along his forearm and out his elbow to ground.
• For this reason, at least one experienced electrical engineer tends to work one-handed on circuits, to minimize a chance electrical connection, and tends to keep his hands behind him in high-voltage situations.