What is the relationship between stress and cross-sectional area during a tensile test?

During a tensile test, stress is defined as the force applied to an object divided by the cross-sectional area over which that force is distributed. Stress is calculated using the formula:

[ \text{Stress} = \frac{\text{Force}}{\text{Area}} ]

As the cross-sectional area decreases, assuming the force remains constant, the value of stress increases because you are dividing the same amount of force by a smaller area. This relationship highlights how materials react differently under load, and it's particularly important in understanding how materials can fail under tension.

When considering the options, recognizing that stress is inversely related to cross-sectional area helps clarify why a reduction in diameter or area results in increased stress. This understanding is crucial for predicting material behavior under load, particularly in structural applications where safety and performance are concerned. Thus, as the diameter reduces, the stress indeed becomes greater, which accurately reflects the correct choice.