A small, brief spark sometimes occurs when plugging an appliance into an electrical outlet due to the rapid draw on the available power. These sparks are perfectly normal and usually not a cause for concern. However, big, lengthy sparks that are accompanied by a burning smell may indicate a serious issue with your electrical system. Other reasons outlets may spark when you plug in appliances include:

• Overloading: Overloading occurs when too many devices are connected to a single outlet or circuit, exceeding its designed capacity. It may lead to wires overheating and cause sparking at the outlet.
• Short-circuiting: Old and outdated appliances may cause short circuits. Plugging in one of these appliances creates a sudden surge of electricity that results in sparks at the outlet as the electrical current moves across the faulty connections.
• Worn-out outlets: Electrical outlets may wear out due to repeated use over time. The contact points inside the outlet may become loose or corroded, leading to poor connections. When a plug is inserted into a worn outlet, poor contact causes arcing and results in visible sparks.
• Moisture: Water exposure from leaks within the walls or a splash may cause the outlet to spark. When water or humidity infiltrates an outlet or appliance, the current flows unexpectedly and results in visible sparks. Installing a GFCI helps protect outlets from water damage by shutting off electrical flow whenever an interruption occurs.
• Improper repairs: A poor repair job by an unlicensed electrician may lead to several safety hazards and electrical problems, including outlet sparking.