“The turning effect of force is called the moment of force or Torque”
It depends upon the following
Moment of a Force About a Point = Force X Perpendicular Distance From Point
τ = F x d
The sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments about that point.
The longer handle of the wrench provides a mechanical advantage to the man. This mechanical advantage is due to the increased leverage obtained from the longer distance between the pivot point (fulcrum) and the point where the force is applied (the end of the wrench handle).
When the man exerts force on the end of the long wrench handle, the torque is produced and it helps to open the bolt easily.