Question

The controlling force curves P, Q and R for a spring controlled governor are shown in the figure, where \( r_1 \) and \( r_2 \) are any two radii of rotation. 

The characteristics shown by the curves are

• A. P – Unstable; Q – Stable; R – Isochronous
• B. P – Unstable; Q – Isochronous; R – Stable
• C. P – Stable; Q – Isochronous; R – Unstable
• D. P – Stable; Q – Unstable; R – Isochronous

Hint:

In a governor mechanism, the isochronous curve maintains a constant time period, while the stable curve results in system stability, and the unstable curve leads to instability.

Answer 1

The Correct Option is B

In a spring-controlled governor:
- Curve P shows an unstable characteristic because the controlling force decreases as the radius increases, which leads to instability.
- Curve Q is isochronous, meaning it maintains a constant time period, independent of changes in speed or radius.
- Curve R is stable, as the controlling force increases with the radius, ensuring stability in the system.
Thus, the correct answer is (B).