_____ is the equation for unsteady state heat conduction through solid materials.

Heat transfer can occur through conduction, convection, and radiation:   Conduction: Heat is transferred from the hotter end of an object to the colder end through physical contact. For example, when you touch a metal cooking pot in an air-conditioned room, your hand loses heat to the colder pot. Convection: Heat is transferred by the movement of a heated fluid, such as air or water. For example, in free convection, warm air or water rises and is replaced by cooler air or water. Radiation: Heat is transferred between objects without direct physical contact through electromagnetic waves.... Show more

Heat transfer can occur through conduction, convection, and radiation:
 

Conduction: Heat is transferred from the hotter end of an object to the colder end through physical contact. For example, when you touch a metal cooking pot in an air-conditioned room, your hand loses heat to the colder pot.
Convection: Heat is transferred by the movement of a heated fluid, such as air or water. For example, in free convection, warm air or water rises and is replaced by cooler air or water.
Radiation: Heat is transferred between objects without direct physical contact through electromagnetic waves. For example, the sun heats the earth through electromagnetic waves. 

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