Imagine the inside of your cordless screwdriver like an electrical circuit. When you pull the speed control trigger, a switch on the inside of the tool’s casing conducts electricity from the rechargeable battery to the motor.
Every time you pull the trigger, you are completing the circuit, allowing power to flow through the screwdriver.
Battery
Every cordless screwdriver has a rechargeable battery.
Motor
The motor converts the battery’s electrical energy into mechanical energy giving the rotation required to turn the chuck.
The motor’s power is a combination of torque and speed.
Gearbox
Power is transferred from the motor to the chuck via the gearbox.
Depending on the make and model of your cordless screwdriver, the gearbox may offer the possibility to select different gears, and therefore speed ranges.
Chuck
The motor’s power causes the chuck, and therefore the bit, to rotate, allowing the cordless screwdriver to drive screws or drill holes.