Question

Two students each build a piece of scientific equipment that uses a 555-mm-long metal rod. One student uses a brass rod, the other an invar rod. What is the difference between the two rods?

1) Brass rod is more conductive than invar rod
2) Invar rod is more conductive than brass rod
3) Brass rod is more resistant to heat than invar rod
4) Invar rod is more resistant to heat than brass rod

Answer 1

The primary difference lies in conductivity and resistance to heat; brass is more conductive, while invar is more resistant to temperature-induced size changes due to its low thermal expansion coefficient.

Step-by-step explanation:

The difference between a brass rod and an invar rod is in their conductive properties and resistance to thermal expansion. Brass is generally more conductive than invar but invar has a very low coefficient of thermal expansion, meaning it does not expand or contract as much as brass with changes in temperature. This makes invar more resistant to heat when it comes to maintaining its size and shape.

The fact that invar has a low coefficient of thermal expansion means it is an ideal material for precision instruments that must maintain their dimensional stability through temperature changes, such as scientific measurement equipment and clocks. On the other hand, due to its superior electrical conductivity, brass is often used for electrical components and conductive parts.