Tensile strain may be measured by the change in electrical resistance of a strain gauge.
A strain gauge consists of folded fine metal wire mounted on a flexible insulating backing sheet.
The strain gauge is firmly attached to the specimen, so that the strain in the metal wire is always identical to that in the specimen.
When the strain in the specimen is increased, what happens to the resistance of the wire?
it decreases, because the length decreases and the cross-sectional area increases
it decreases, because the length increases and the cross-sectional area decreases
it increases, because the length decreases and the cross-sectional area increases
it increases, because the length increases and the cross-sectional area decreases