Thermal conductivity of a material may be defined as the

• A. All of these
• B. Quantity of heat flowing in one second through one cm cube of material when opposite faces are maintained at a temperature difference of 1°C
• C. Quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
• D. Heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces

Answer: (A)