If you leave an electric switch turned on when nothing is plugged into it, it is dangerous, especially if it gets wet.

The claim can be broken down into two parts: first, whether leaving an electric switch turned on when nothing is plugged into it is dangerous; second, whether it becomes especially dangerous if it gets wet. Regarding the first part, electrical theory and expert explanations confirm that if no device is plugged in, the circuit is open and no current flows, so the switch being on alone does not pose a danger.

However, some power strips or switches with indicator lights may draw a small amount of power even when no device is connected, but this is generally not hazardous. The second part of the claim about wetness increasing danger is supported by multiple sources. Water can cause electrical faults such as short circuits or leakage currents in switches or outlets, which can lead to shocks or fires.quora.comquora.comShould I call an electrician if the light switch got wet and it’s now giving...briggselectrical.com.aubriggselectrical.com.au4 things you need to do if an electrical outlet gets wetsustainability.stackexchange.comsustainability.stackexchange.comenergy - Do switchable sockets left "on" use electricity if there's nothing...

A wet switch that gives shocks indicates a fault that could be lethal and requires immediate attention.quora.comquora.comShould I call an electrician if the light switch got wet and it’s now giving... While touching a dry switch with wet hands is unlikely to cause shock unless water has penetrated inside, water intrusion into the switch mechanism itself creates a real hazard.

Therefore, the claim that leaving a switch on with nothing plugged in is dangerous only holds true if the switch or wiring becomes wet or damaged. Under normal dry conditions, it is not inherently dangerous. The verdict is mostly true because the danger arises primarily from water exposure rather than simply leaving the switch on without load.