Voltage can exist between hot and ground due to capacitive coupling, where the human body or testing device acts as one electrode of a capacitor, and grounded surfaces serve as the other. When using a neon testing screwdriver, the bulb lights up because a small current flows through this capacitance, even if the user is not directly grounded. The neutral wire is typically grounded at the switchboard, creating a potential difference between hot and ground. The circuit is effectively closed through this capacitive interaction, allowing for voltage detection without a direct ground connection. Understanding this principle clarifies how electrical testing devices can indicate voltage presence in various environments.
