Why Do Wall Switches Produce Sparks When Plugged In Or Unplugged?

When an appliance plug touches the metal contacts in the Wall Switch circuit, a current is instantly established through the air. At this moment, the voltage difference and conductivity conditions cause the air to break down, producing a brief electric arc.

The cause of this spark may be poor internal contact. The metal contacts inside the switch or socket may be aged, loose, or oxidized, resulting in an unstable contact surface. When the plug is first inserted, the current is concentrated and its flow direction changes rapidly, easily causing a momentary discharge and thus a spark.

A similar phenomenon can occur when the plug is removed. Before and after the plug is disconnected from the contacts, the tiny distance between the metal parts is still sufficient for a current jump. If the removal process is rapid and the conductor impedance is low, the charge can flow through the air, generating an electric arc.