What is the default effort applied in case of Joint_effort_controller?

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I saw in a web forum that there are three options for effort_controllers

effort_controllers 1)joint_effort_controller 2) joint_position_controller 3) joint_velocity_controller

in case of (2) the joint_position_controller it seems that the default position is the position of the description of the robot. So if we select joint_effort_controller, what would the default effort that will be applied to the joints and , is it possible to specify these initial controller inputs in the launch files?