Why is graphite used instead of gold or copper wires to conduct electricity in very hot situations such as an industrial kiln?

In very hot situations like an industrial klin, there is risk of melting of wires if they are made up of metal with low melting point. Also, metal with high electrical conductivity is required under such situations.

Graphite is good conductor of heat and electricity also, it has very high melting point therefore, it is used instead of copper and gold with low melting point to make wires.

Other advantages of graphite are it is thermal shock resistant, The coefficient of thermal expansion is 3 times less than that of copper. The melting of graphite does not take place and it gets converted directly from solid to liquid at 3400 °C (extremely high temperature). It forms lighter electrode because density of graphite is 5 times less than that of copper.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.