What device is used to measure changes in the length of an object?

What device is used to measure changes in the length of an object?

• A. A ruler
• B. An extensometer
• C. A caliper
• D. A tape measure

Answer: (B)

Measuring how much an object changes in length under load is about tracking deformation. An extensometer is the instrument built for that purpose: it attaches to a specimen and monitors the relative movement between two points, giving you the change in length (ΔL) and, from that, the strain ε = ΔL/L0. This makes it ideal for precise measurement of elongation or contraction during tests. Other devices serve more general or static length measurements. A ruler provides a fixed length and isn’t sensitive to small changes; a caliper measures a single external dimension at a given size; a tape measure is for longer distances and lacks the precision needed to track small deformations. In material testing, the extensometer provides the accurate data on how length changes as the material is stressed.

Measuring how much an object changes in length under load is about tracking deformation. An extensometer is the instrument built for that purpose: it attaches to a specimen and monitors the relative movement between two points, giving you the change in length (ΔL) and, from that, the strain ε = ΔL/L0. This makes it ideal for precise measurement of elongation or contraction during tests.

Other devices serve more general or static length measurements. A ruler provides a fixed length and isn’t sensitive to small changes; a caliper measures a single external dimension at a given size; a tape measure is for longer distances and lacks the precision needed to track small deformations. In material testing, the extensometer provides the accurate data on how length changes as the material is stressed.