Everyone who deals with screws and screwdrivers knows that long screwdrivers are stronger than short ones. However, I can't find any relationship between length of a screwdriver and mechanical advantage. For a wrench, it's obvious: Long arms produce more torque. But in case of a screwdriver, it is not so simple.
For this question, my point is not originally about screwdrivers. I'm actually going to design a simple machine that has a relatively long arm connected to an electric motor. It's intuitive that the long arm weakens the motor (Or maybe I'm wrong?). The answer of my question about screwdrivers will help me undrestand the mechanism behind this case, and solve the problem.