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4. (10pt) Two strain gauges are mounted so that they sense axial strain on a steel member inuniaxial tension. The 120 2 gauges from two legs of a Wheatstone bridge,

and are mounted onopposite arms. Assume all resistors are equal when the strain gauge circuit is initially balancedwith no load. 1) (5pt) For an excitation voltage of 4V and a bridge output voltage of 120 µV under load,estimate the strain in the member. ) (5pt) What is the resistance change experienced by each gauge? The gauge factor foreach of the strain gauges is 2 and Em for this steel is 29 x 106 psi.

Fig: 1

Fig: 2

Fig: 3