False: A differential screw is not defined as a mechanical device consisting of two screws connected in parallel.

Explanation:
A differential screw, also known as a micrometer screw or a differential screw jack, is a mechanical device that consists of two screws that are not connected in parallel. Instead, they are connected in series, meaning that the movement of one screw is translated into a different movement for the other screw.

Function and Design:
The main function of a differential screw is to provide precise and controlled linear motion. It is commonly used in applications where fine adjustments or precise positioning is required, such as in scientific instruments, optical devices, and machinery.

The design of a differential screw typically consists of a larger screw, called the lead screw or input screw, and a smaller screw, called the follower screw or output screw. These two screws are threaded in opposite directions and have different pitch values.

Working Principle:
When a rotational force is applied to the lead screw, it causes linear motion along the length of the screw. This linear motion is then translated to the follower screw, which moves in the opposite direction due to the opposite threading.

The differential screw works based on the principle of mechanical advantage. The pitch difference between the two screws determines the mechanical advantage or the ratio of linear displacement between the input and output screws. By adjusting the rotational motion of the lead screw, precise and controlled movement can be achieved with the follower screw.

Advantages:
Some of the advantages of using a differential screw include:

1. Precise and controlled linear motion: The design of the differential screw allows for fine adjustments and precise positioning.
2. Mechanical advantage: The differential screw provides a mechanical advantage that allows for a small rotational input to produce a larger linear output.
3. Compact and simple design: The differential screw is a relatively simple device that can be compact in size, making it suitable for various applications.
4. High load capacity: The design of the differential screw allows for high load capacities due to the mechanical advantage provided.

Conclusion:
In conclusion, a differential screw is not defined as a mechanical device consisting of two screws connected in parallel. Instead, it is a device that consists of two screws connected in series, allowing for precise and controlled linear motion.