Question

A good insulator of heat is:
(A) Copper
(B) Mercury
(C) Trapped air
(D) Iron

Answer 1

Hint:Here we have to know about metals, non-metals, insulators and conductors. Almost all metals are good conductors of heat and electricity.

Complete step by step answer:
Metals: Metals are opaque, lustrous elements and are strong conductors of heat and electricity. Most metals are malleable and ductile and are generally denser than other substances. When small loads are added to metals, they bend and revert to their original shape when the load is lifted. Bending a sheet of steel is an example where the ties are bent or strained by just a small percentage. This is called elastic deformation.

Nonmetals: Non-metals are those that do not have all the metallic characteristics. They are strong thermal and electrical insulators. They are mainly gases and occasionally liquids. Many of them are also solid at room temperatures such as carbon, sulphur and phosphorus.

Insulators: The insulator is a substance that does not conduct electrical currents. Isolating materials include paper, plastic, rubber etc. Vacuum is also an insulator but not really a material. Insulation is used in most electrical conductors.

Conductors: Conductors are the materials or substances which permit heat and electricity to course through them. They conduct heat and electricity since they permit electrons to stream effectively inside them from particle to molecule. Also, conductors permit the transmission of light starting with one source then onto the next.

Almost all the options given in the question are metals except trapped air. So, they can conduct heat and electricity. Hence option C is correct.

Note:We may get confused between mercury and trapped air. But mercury can somewhat act as a conductor in solid state.