remains unchanged
decreases
With rise in temperature, the Young's modulus of elasticity generally decreases for most materials.
Young's modulus (E) is defined as the ratio of stress to strain in the elastic region of a material. It is a measure of the stiffness of a material. The temperature dependence of Young's modulus is related to the interatomic bonding forces and thermal expansion of the material.
Step 1: Understand the relationship between interatomic forces and Young's modulus.
Young's modulus is given by \( E = \frac{\text{Stress}}{\text{Strain}} \). At the atomic level, it depends on the curvature of the potential energy curve between atoms: \( E \propto \frac{d^2U}{dr^2} \), where U is the interatomic potential and r is the interatomic distance.
Step 2: Consider the effect of temperature on interatomic spacing.
As temperature increases, materials expand due to increased atomic vibrations. This increases the average interatomic distance (r). For most bonding potentials, the second derivative \( \frac{d^2U}{dr^2} \) decreases as r increases beyond the equilibrium position.
Step 3: Analyze the effect on bond stiffness.
The force constant (k) of the atomic bond, which determines Young's modulus, decreases with increasing interatomic separation. Since thermal expansion causes increased interatomic spacing, the bond becomes less stiff, resulting in a decrease in Young's modulus.
Step 4: Consider exceptions and general behavior.
While most materials show a decrease in Young's modulus with increasing temperature, some materials like invar (a nickel-iron alloy) show minimal change due to their near-zero thermal expansion coefficient.
Therefore, with rise in temperature, the Young's modulus of elasticity decreases for most materials.
A black body is at a temperature of 2880 K. The energy of radiation emitted by this body with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant, b = 2.88×106 nm-K. Then,


\( x \) is a peptide which is hydrolyzed to 2 amino acids \( y \) and \( z \). \( y \) when reacted with HNO\(_2\) gives lactic acid. \( z \) when heated gives a cyclic structure as below:

What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)