Flat spiral springs: which of the following statements correctly describe their construction and use?

Introduction / Context:
Flat spiral springs are energy-storage devices used in timing mechanisms, measuring instruments, and recoil systems. Understanding their geometry and support/torque application helps in correct specification and design.

Given Data / Assumptions:

• The spring is a uniform thin strip (constant thickness and width) wound into a planar spiral.
• One end is fixed (often the outer), the other is attached to a hub or arbor to receive torque.
• Applications include clocks, watches, spring balances, and meters.

Concept / Approach:
Under applied torque, the spiral stores strain energy by bending along its length. Because the strip is thin, bending dominates over torsion, enabling a compact form that delivers nearly constant torque over limited rotations.

Step-by-Step Solution:
Identify the element: a thin rectangular strip forms the spring.Fixity/support: typically the outer end is anchored to the casing; the inner end connects to a rotating arbor.Load application: a torque winds or unwinds the spiral, bending the strip and storing energy.Use cases: timekeeping mechanisms and measuring devices rely on predictable torque–deflection behavior.

Verification / Alternative check:
Device teardown or catalog drawings for watches and gauges consistently show a flat spiral strip with outer-end anchorage and inner-end arbor connection.

Why Other Options Are Wrong:

• Options (a), (b), and (c) are each correct; hence the correct combined choice is 'All of the above'.

Common Pitfalls:

• Confusing flat spiral springs with helical torsion or clock springs having different winding and support arrangements.

Final Answer:
All of the above.