Which of the following metals is used for making jewelry?

Give a reason why electrical wires are coated with plastic.

Which among the following statements is incorrect for magnesium metal?

An electrolytic cell consists of:
$(i)$ Positively charged cathode
$(ii)$ Negatively charged anode
$(iii)$ Positively charged anode
$(iv)$ Negatively charged cathode

Four groups are given linking a metal, its ore, and the chemical formula of the main component of the ore. How many of these are correct?
$(1)$ Iron - Magnetite - $Fe_{3}O_{4}$
$(2)$ Iron - Siderite - $FeS_{2}$
$(3)$ Copper - Copper glance - $Cu_{2}S$
$(4)$ Copper - Dolomite - $Al_{2}O_{3}$

Compound $X$ and aluminium are used to join railway tracks.
$(a)$ Identify the compound $X$.
$(b)$ Name the reaction.
$(c)$ Write down its chemical reaction.