# Second Year Physics Physics of Solids

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$17.5 What is meant by strain energy? How can it be determined from the force-extension graph?$

$17.4 What stress would cause a wire to increase in length by 0.01 \% if the Youngs modulus of the wire is 12 \times 10^{10} \mathrm{~Pa} . What force would produce this stress if the diameter of the wire is 0.56 \mathrm{~mm} ?(Ans: 1.2 \times 10^{8} \mathrm{~Pa} 2.96 \mathrm{~N} )$

$17.11 What is meant by hysteresis loss? How is it used in the construction of a transformer$

$17.6 A cylindrical copper wire and a cylindrical steel wire each of length 1.5 \mathrm{~m} and diameter 2.0 \mathrm{~mm} are joined at one end to form a composite wire 3.0 \mathrm{~m} long. The wire is loaded until its length becomes 3.003 \mathrm{~m} . Calculate the strain in copper and steel wires and the force applied to the wire. (Youngs modulus of copper is 1.2 \times 10^{11} \mathrm{~Pa} and for steel is 2.0 \times 10^{11} \mathrm{~Pa} ).(Ans: 1.25 \times 10^{-3} 7.5 \times 10^{-4} 477 \mathrm{~N} )$

$17.3 A wire 2.5 \mathrm{~m} long and cross-section area 10^{-5} \mathrm{~m}^{2} is stretched 1.5 \mathrm{~mm} by a force of 100 \mathrm{~N} in the elastic region. Calculate(iii) the energy stored in the wire.$