1.

A metal rod of Young's modulus and coefficient of thermal expansion alpha is held at its two ends such that its length remains invariant. If its temperature is raised by t^(@)C, the linear stress developed it its is .....

Answer»

`(alpha t )/(F)`
`(Y)/(alpha t)`
`Y prop t `
`(1)/(Y prop t)`

Solution :`DELTA l = alpha l Delta T`
`therefore (Delta l )/(l) = alpha Delta T ""...(1)`
YOUNG modulus `Y = ("stress" SIGMA _(l))/("STRAIN" G_(l))`
`therefore epsi _(l ) = (sigma _(l))/(Y)`
`therefore (Delta l )/(l) = (sigma _(l))/( Y) ""...(2)`
From equation (1) and (2)
`(sigma _(1))/(Y) = alpha Delta T`
`therefore sigma _(l) = Y prop Delta T`
`therefore sigma _(l) = Y prop T` (where `Delta T =l ^(@)C)`


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