Practical Material Testing

Try these questions

5 questions from this lesson’s quiz. Start the lesson to answer them and see the right answers.

1. 1. In a Searle's apparatus experiment, why is a reference wire hung beside the test wire?

   • A. To carry the extra slotted masses so the test wire does not stretch
   • B. To cancel the effect of thermal expansion caused by room temperature changes
   • C. To increase the cross-sectional area that carries the load
   • D. To measure the diameter of the test wire

2. 2. A steel wire has a cross-sectional area of 4.0 x 10^{-7} m^2 and an original length of 2.0 m. A tensile force of 40 N extends it by 1.0 mm. Calculate Young's modulus of the steel in GPa.

   Type your answer (in GPa) in the lesson.

3. 3. An ungalvanised mild steel cable on a footbridge in a humid valley slowly corrodes. The traffic load stays the same. What happens to the tensile stress in the cable?

   • A. It decreases because the cable becomes lighter
   • B. It stays the same because the force is constant
   • C. It increases because the cross-sectional area becomes smaller
   • D. It becomes zero because the cable is no longer elastic

4. 4. Which mechanical property of steel cables gives visible stretching as a warning before they fracture?

   Type your answer in the lesson.

5. 5. After a wire extension test, the load is removed but the vernier reading does not return to its original zero. What does this show?

   • A. The wire went beyond its elastic limit and has plastic deformation
   • B. The wire has a very high Young's modulus
   • C. The spirit level was perfectly balanced
   • D. The reference wire has stretched more than the test wire

More in Mechanical Properties of Materials

• ▸Understanding Tensile Strain
• ▸Modulus of Elasticity and Young's Modulus
• ▸Stress Strain Curves and Material Failure
• ▸Industrial Applications of Material Properties
• ▸Concept of Temperature and Temperature Scales
• ▸Liquid Expansion and Mechanical Thermometers
• ▸Electrical Temperature Sensing
• ▸Thermal Expansion in Solids

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