Which of the following substance is a bad conductor of electricity but a good conductor of heat?

The correct answer is Mica.

Key Points

• Mica is a good conductor of heat but had a bad conductor of electricity.
• Mica has good thermal conductivity due to phonons but doesn't have sufficient free electrons to be a good conductor of electricity.
• Micas have sheet structures whose basic units consist of two polymerized sheets of silica (SiO4) tetrahedrons.
• Of the 28 known species of the mica group, only 6 are common rock-forming minerals. Muscovite, the common light-coloured mica, and biotite, which is typically black or nearly so, are the most abundant.

Additional Information

• Asbestos and celluloid are also good electrical insulators, but they are not good conductors of heat.
• Asbestos is a fibrous mineral that was commonly used as insulation before it was discovered to be carcinogenic. Celluloid is a plastic material that was used for films and other products before it was replaced by safer materials.
• Sand is a poor conductor of both electricity and heat.