Electrons are particles with very special nature. They behave as a matter with mass and speed and when collide with other particles they produce heat. Another nature of electrons is the magnetic field that accompanies the electrons when they change their direction. This unique nature that is not found in any other particles rather than electrons do the real magic.
So electrons don't vanish after being used but rather they return back to their original sender after doing the required work. They are like labors with special skills when their manager sends them for a special task by giving them some incentives and they return back again to the same manager after they finish their assigned task when he can send them back to another task with the appropriate incentives.
For example if we need a motor to rotate, the power supply (The manager) asks the motor (the client) about how much labor it needs to rotate for a second. The motor calculates this through measuring how much rotating force it needs to overcome the mechanical resistance of the rotating parts and then rotate them with the needed speed.
Knowing that moving electrons in a magnetic field yields a rotating force what now is needed is sending the correct amount of electrons (labors) for this second that are capable of producing the needed rotating force when they cut the internal magnetic field of the motor. This amount of electrons in one second is the current intensity and to continue for more seconds the power supply (the manager) should have the power to send the same amount every second so it should have the needed incentives to force (persuade) the required amount of electrons to go to the client and do the required job.
The incentives can be also another magnetic field but this time applied at the electrons in the power supply (the manager puts their labor in a very tense situation that forces them to go forward) this magnetic field is applied on the electrons while they are rotating using another form of energy like water falls or pressured water-vapour.
To continue sending the electrons (the labors) the manager must continue paying the incentives (Boiling water for example to produce water vapour). That is why we need to consume some type of energy to produce electrical energy.