YM1 Pupil Sheet

YM1 Pupil Sheet - Activity YM1 NAME Pupil Sheet Youngs...

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Activity YM1 Pupil Sheet NAME………………………………………………………………………… Young’s Modulus Experimental details The device used in this experiment to determine Young’s Modulus and Poisson’s ratio is the electrical resistance strain gauge. This is the most widely used device for measuring elastic strains. It is essentially a strip of metal foil which is firmly glued to the surface where the strain is to be measured, so that when the material is strained, the strain at the surface is fully transmitted to the metal foil. Elastic strain along the length of the strip causes a small change in resistance of the gauge, largely because of the change in length and cross- sectional area of the strip, although there is also a slight change in its resistivity. Small changes in resistance are easy to measure accurately, and so the gauge gives an accurate reading of the small elastic strain along the direction of the strip in the gauge. The change in resistance, and hence the voltage across the strain gauge for a constant current, is proportional to the strain; the gauge manufacturer supplies the value of the constant of proportionality. For the strain gauges and current used here ε = 3.803×10 -7 V (a conversion factor provided by the manufacturer), where ε = strain (No units – a dimensionless quantity) and V = voltage across strain gauge (measured in microvolts). This practical uses a simulation, based on a University experiment, of the simple cantilever bending of the beam to which the strain gauges are attached. The sidearm is not used in this experiment. Identify the 3 strain gauges on the cantilever arm. For this experiment you will use only two gauges; the one that is lined up along the cantilever, the “x” direction and the one lined up laterally across the cantilever, the “y” direction. These are represented in the diagram, above, by the strain gauges on the left and right respectively. Measurements are taken using a single meter, which is attached in turn to
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YM1 Pupil Sheet - Activity YM1 NAME Pupil Sheet Youngs...

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