alleryOn the stress-strain curve of a ductile material, the **proportional limit** is the point up to which
AHooke's law is obeyed
Bthe wire breaks
Cplastic deformation begins
Dthe material loses all elasticity
Answer & Solution
Correct answer: A. Hooke's law is obeyed
Below the proportional limit, stress is directly proportional to strain ($\sigma = Y\varepsilon$) — i.e. Hooke's law holds.
Past it, the curve still rises but is no longer linear.
The elastic limit (slightly higher) marks where deformation becomes irreversible.
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