Physics · Mechanical Properties Of Solids · NEET
It decreases for nearly all materials. When you heat a solid, its atoms vibrate more and the bonds between them become easier to stretch. So the same force produces a larger strain, which means a smaller Young's modulus and lower elasticity. In short: heat makes a material more plastic (easier to deform permanently) and less elastic.
Yes. Young's modulus Y = stress / strain, and for a heated material the same stress gives more strain, so Y falls. This is why NEET treats 'elasticity decreases with temperature' as the same idea as 'Young's modulus decreases with temperature'. They are two ways of saying the material got softer.
Heating raises the average distance and vibration of atoms, weakening the interatomic bonds. Weaker bonds resist deformation less, so the metal bends and stretches more easily. Blacksmiths use exactly this: they heat iron so it can be hammered into shape, then cool it to restore stiffness.
Yes. Cooling strengthens the bonds, so the wire returns to shape more strongly and has a higher Young's modulus. This is why very cold metals are stiffer and more brittle. Remember the hook: Cold = stiff (more elastic), Hot = soft (less elastic).
INVAR, an alloy of iron and nickel (about 36% Ni). Its elasticity and length stay almost constant even when temperature changes. Because of this it is used where dimensions must not change with heat, such as pendulum clocks, measuring tapes and precision instruments.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
For almost all materials, elasticity decreases as temperature increases and increases as temperature decreases. Equivalently, Young's modulus falls on heating and rises on cooling.
Heat increases atomic vibration and average bond length, which weakens interatomic forces. Weaker bonds mean the same stress produces more strain, lowering Y = stress/strain.
Yes, INVAR (an iron-nickel alloy). Its elastic properties and length are nearly independent of temperature, so it is used in precision clocks, meter scales and scientific instruments.
Thermal expansion is the change in size with temperature. The effect of temperature on elasticity is the change in stiffness (Young's modulus). Both come from atomic vibration but describe different properties; the next concept, thermal stress in a clamped rod, links them.
NEET regularly asks conceptual one-liners such as 'On heating, elasticity of a material...' The safe answer is 'decreases'. Knowing the INVAR exception protects you from tricky assertion-reason questions.
