What effect does changing the RPM of two diagonal motors on a quadcopter have?

Changing the RPM of two diagonal motors on a quadcopter primarily induces yaw, which refers to the rotation of the aircraft around its vertical axis. In a quadcopter, each motor's RPM contributes to the overall thrust and stability of the drone. By increasing the RPM of one pair of diagonal motors while decreasing the RPM of the other pair, the quadcopter will experience a differential thrust that causes it to rotate clockwise or counter-clockwise.

This rotational movement is critical in maneuvering the quadcopter during flight, allowing it to turn in place or adjust its orientation without requiring translational movement forward or backward. The ability to control yaw ensures that the pilot can navigate the drone effectively and maintain its intended flight path.

The other effects mentioned, such as climb, roll, and descent, would typically result from changes in overall thrust or adjustments to lateral motor pairs, but not necessarily from the specific change in RPM of diagonal motors. Thus, altering the RPM of diagonal motors specifically affects the yaw axis, making it the correct answer in this context.