In a robot manipulator, what is the primary function of the joints?

• A. Joints adjust the alignments of the robot automatically.
• B. Joints provide relative motion between links.
• C. Joints convert chemical energy to electrical energy.
• D. Joints determine the color of the robot.

Answer: (B)

Joints are the connection points between links that allow one link to move relative to the next. This relative motion—rotation for hinge-like joints or translation for sliding joints—gives the manipulator its reach and ability to orient the end effector in 3D space. The other options describe effects not provided by joints: alignment changes are handled by actuators and control systems, energy conversion occurs in power electronics, and color is just appearance.