Mica is used in cooking utensil because it is

Thermal conductivity (how well a material transfers heat) and electrical conductivity (how well it carries electric current) are independent physical properties: a material need not have both or neither — some substances conduct heat readily while resisting current flow, and vice versa.

Mica is exactly such a material. Its layered crystal structure lets heat pass through it easily, making it a good conductor of heat, while it has essentially no free electrons available to carry current, making it a poor conductor (an insulator) of electricity. This is precisely the combination needed inside a heat-generating cooking/heating utensil such as an electric iron, toaster, or hot-plate: the mica sheet must let the heat produced by the internal coil pass through to the cooking or pressing surface, while blocking the coil's live current from reaching the outer casing the user touches.

• Good conductor of both heat and electricity would let the coil's live current reach the outer casing along with the heat, risking an electric shock the moment the utensil is touched.

• Bad conductor of heat but good conductor of electricity would carry the coil's current to the casing while barely letting the intended heat escape — unsafe and useless for heating at the same time.

• Bad conductor of both heat and electricity keeps the user safe from shock but also blocks the very heat transfer the utensil exists to provide.

Only mica's good-heat/poor-electricity combination lets it perform both jobs at once — transmit the required heat while insulating against shock — which is why it is used in such utensils.

In strict materials-science terms mica's absolute thermal conductivity is modest, but relative to its very poor electrical conductivity it behaves as by far the better heat conductor of the two — this heat-good/electricity-poor comparison is exactly what the officially published UPTET Paper II answer key (2017 and 2021) tests and confirms.