Can a relay be plugged in wrong?

Yes, a relay can be plugged in incorrectly, particularly if it has a specific orientation or pin configuration. If the relay is inserted in the wrong direction or in the wrong socket, it may not function properly or could potentially damage the relay or the circuit. It's important to consult the relay's datasheet or markings to ensure correct installation. Always ensure that the power is off before connecting or disconnecting a relay to prevent electrical hazards.