Correct option is D
All insulating materials, also known as dielectric materials, share the primary characteristic of having a high resistance to the flow of electric current.
Features and properties common to insulating materials: -
High Electrical Resistance: Insulators have very high electrical resistance, often many orders of magnitude higher than conductive materials. This property prevents the easy flow of electric current through the material.
Low Conductivity: Correspondingly, insulators exhibit very low electrical conductivity. Their ability to conduct electric charge is minimal compared to conducting and semiconducting materials.
Dielectric Strength: Insulating materials have a property known as dielectric strength, which is a measure of the electrical strength of a material as an insulator.
Electrical Insulation: By virtue of their high resistance and low conductivity, insulating materials are used to prevent unwanted flow of current, to isolate electrical components, and to ensure the safety of electrical circuits by preventing short circuits and protecting against electric shock.
High Resistivity: Resistivity is a material property that quantifies how strongly a material opposes the flow of electric current. Insulators have high resistivity values, indicating their effectiveness in resisting current flow.
Minimal Free Electrons: The atomic structure of insulating materials typically features electrons that are tightly bound to their respective atoms and not free to move across the structure. This contrasts with conductors, where electrons can move more freely, facilitating electrical conduction.
Temperature Dependence: The insulating properties of materials can change with temperature. For many insulators, as temperature increases, they might become slightly more conductive (though still very poor conductors) because thermal energy can liberate some electrons from their bound states.
(a) a low resistivity but high conductivity: This is incorrect because insulating materials are defined by their high resistivity and low conductivity.
(b) a positive temperature coefficient of resistance: This is incorrect for insulating materials. A positive temperature coefficient of resistance means that resistance increases with an increase in temperature, which is typical for conductors, not insulators.
(c) no effect of temperature: This is incorrect because the resistance of insulating materials does change with temperature, generally decreasing as temperature increases.
(d) a negative temperature coefficient of resistance: This is correct. Most insulating materials have a negative temperature coefficient of resistance, meaning their resistance decreases as temperature increases.
Therefore, the correct answer is (d) a negative temperature coefficient of resistance.
