The tip of the coil slides over the end of the coil very easily.
The knob at the bottom adjusts the voltage produced at the tip. This knob should NOT be used to turn the coil on and off as it will damage the coil if adjusted while running.
The on/off switch is a rather inconspicuous silver button on the side. It makes no clicking sound or any other indication that it has been turned on. It also functions as the off switch. It is recommended that the instructor take time before class to familiarize themselves with the button.