The force required to turn a screwdriver can be reduced by?

How wide the screw is, How long the screw is, and What kind of material you are screwing something into.

The force required to turn a screwdriver can be reduced

by making the handle of the screwdriver fatter.

The torque applied to turning the screw is (the force you apply

to the outside of the handle) multiplied by (the radius of the handle,

away from the central shaft).

By making the radius of the handle larger, you increase the torque

applied to turn the screw.