Question

Iron rims are heated red hot before planting on cart wheels. Why?

Answer 1

Hint: To solve this problem we should learn about the properties of metal, and the concept of thermal expansion and hence by using this information we can easily understand and approach our answer to this question logically.

Complete step-by-step solution -
Metals having properties like lustrous, malleable, ductile, good conductor of heat and electricity. Metals have potential to withstand hammering and can be made into thin sheets known as foils also they can draw into wires.
Change in shape, area, volume, and density in reaction to change in temperature, usually not including phase transition of matter is known as thermal expansion
The iron or steel is heated and expanded, a flat band of iron or steel is made into a hoop shape. It is then rapidly cooled and shrinks back into normal, non heated size and grips the wheel so tightly that it cannot be removed.

Iron rims are made slightly compact than the wheels. On heated red hot before adjusting it on the cart wheels to expand them so that they can be easily fixed on the wheels and water is poured on them to cool them, the rims cool, shrink and take the shape of the wheel and get firmly fixed on the wheels.

Note: The property of metal is to expand on heating and contract on cooling. Expansion as well as contraction of a metal is reversible change, when it cools, it contracts and presses tightly on to the wheels, hence iron rims are heated before being fixed in a cart wheel.