What should the voltage reading be across an open switch of an energized electrical circuit?

In an energized electrical circuit, when a switch is open, it means that the circuit is incomplete and current is not flowing. However, the voltage potential across the open switch is equal to the applied voltage. This is due to the nature of electrical circuits; when no current is flowing, the potential difference (voltage) remains across the open points of the circuit. Therefore, you would measure the full voltage level supplied by the power source across the open switch.

This principle is key in understanding how open and closed circuits function. In a closed circuit, the switch allows current to flow, and you would measure a lower voltage across the switch due to the resistance of the closed circuit path. Conversely, with an open switch, the lack of current results in the full voltage being present across the break in the circuit.