What can cause a spark when a motor's plug is pulled from an outlet

If you are plugging/unplugging under load it means that there is some abrupt energy change causing a spark. Inductors (motors) try to prevent changes in current. So if you unplug one while on it will spark. Capacitors try to prevent changes in voltage. So if you plug something in with a switchmode supply, it will spark as the input capacitors try to quickly charge. If the outlet is sparking when the appliance is off, or when the plug is not being handled, then you have a fire hazard. Cut power to that circuit at the breaker. Replace the outlet or call an electrician.

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