the effort is where u put work into the screwdriver- the handle.
The Effort (or moment) Arm of a screwdriver would be the largest radius of the handle frop the center, ie. the radius of a cylinder. You can use any unit vector along a radius, because they will all yield the same torque (or moment).
A screwdriver is a kind of simple machine called a lever, specifically a class one lever. The handle of the screwdriver acts as the effort arm, the shaft as the fulcrum, and the tip as the load arm, allowing you to apply force to turn screws more easily.
The strength of your arm is the applied force on a screwdriver.
It's a first-class lever, with a very long effort arm and a very short load arm.
Third class.
load arm, effort arm, load, effort, fulcrum!
The longer the effort arm of a lever, the less effort force is needed to lift a load. This is because a longer effort arm increases the leverage, allowing a small effort force to lift a greater load. Conversely, a shorter effort arm requires a greater effort force to lift the same load.
If it is the factory style wiper arm (replacement or otherwise), it probably has a tricky little lock mechanism holding it to the shaft sticking out of the cowling. Take a flat blade screwdriver and pry it in the direction away from the axis of the shaft. It will only move approx 1/4" and this unlatches the arm from the shaft. At this point, it's a matter of carefully prying the arm up off the shaft using whatever prying scheme you can think of without breaking the windshield, bending arms, or doing other damage. Once you get the arm off, inspect the end of it carefully and you'll see the little *&^%%$$$ that was causing you the problem.
THE PRODUCT OF EFFORT AND EFFORT ARM IS CALLED MOMENT OF EFFORT.
With a screwdriver
Effort Arm
A lever with a longer effort arm and a shorter resistance arm would have more mechanical advantage. In this case, if you increase the effort arm to 7 inches while keeping the resistance arm at 3 inches, the mechanical advantage would increase. This is because a longer effort arm allows for less force to be applied to overcome a greater resistance.