Poissons ratio of the soft iron

Question

Question 1: A thin circular wire of the soft iron has a gauge factor of 3.8. What is the Poisson’s ratio of the soft iron?

Question 2: The wire in a strain gauge is 0.1 m long and consists of an initial resistance of 1.20Ω. On application of a force, the wire length rises by 0.1mm and resistance rises by 0.21Ω. What is the gauge factor of the device?

Question 3: A strain gauge containing a resistance of 500Ω and a gauge factor 3.0 is bonded on to a member of structure beneath tensile stress. What is the percentage strain suffered by the member if the change in the resistance of the gauge is accurately measured as 1.5Ω.

Question 4: The resistance strain gauge is employed to measure the stress on steel. The steel is stressed to a 1400 kgf/cm². Suppose Young’s modulus of the steel is 2.1×10⁶ kgf/cm². Compute the percentage change of resistance of a strain gauge supposing gauge factor equivalent to 2.

Question 5: A strain gauge with gauge factor of 2 is fastened to the metallic member subjected to a stress of 1000 kg/cm². The modulus of elasticity of metal is 2×10⁶ kg/cm². Compute the percentage change in resistance of the strain gauge. Determine the value of Poisson’s ratio?

Question 6: A strain gauge containing a resistance of 200Ω and gauge factor 2.5 is joined in series with a blast resistance of 400Ω across a 24V. Find out the change in output voltage when a stress of 140 MN/m² is applied. Modulus of elasticity is 200 GN/m².

Question 7: A resistance wire strain gauge employs a soft iron wire of small diameter. The gauge factor is + 4.2. Neglect the piezo resistive effects; compute the Poisson’s ratio.

Question 8: A compressive force is applied to a structural member. The strain is 5 micro-strains. Two separate strain gauges are joined to the structural member, one is a nickel wire strain gauge having a gauge factor of –12.1 and the other is nichrome wire strain gauge containing a gauge factor of two. Compute the value of the resistance of the gauges after they are strained. The resistance of strain gauges before being strained is 120 Ω.