Question

What is the S.I. unit of heat?
${\text{A}}{\text{.}}$ Dyne
${\text{B}}{\text{.}}$ Erg
${\text{C}}{\text{.}}$ Joule
${\text{D}}{\text{.}}$ Newton

Answer 1

Hint- Here, we will proceed by defining the term heat in reference to the temperature change occurring. Then, we will write down the basic formula for heat transfer. Finally, we will discuss the unit of heat transfer.

Step-By-Step answer:
A portion of the energy may be released into the surrounding in the form of heat in chemical reactions. But this internal energy is not a solid substance or a fluid that the object contains. It's simply the potential energy contained in the bonds that binds particles together within the body. The type this energy occupies as it is transferred between systems and surroundings is heat or thermal energy. This is neither a conserved product nor a conserved gas. Heat is a source of energy that can be transferred or even produced from one body to another, at the cost of losing other types of energy.
Temperature is a measure of a substance 's capacity to transfer heat energy to another physical system, or more generally of any physical system. When two objects (or a system and its surroundings) have different temperatures, then they have different heat transfer capabilities. Over time the energy transfer from the hotter object to the cooler object would transfer. This energy flow is called heat. The heat flow induces cooling of the hotter body, and heating of the colder object. The heat flow will proceed until the same temperature is reached. The two objects have formed a thermal equilibrium between themselves at this point.
The basic formula for heat transfer is given by
$\Delta {\text{Q}} = {\text{mc}}\Delta {\text{T}}$ where $\Delta {\text{Q}}$ denotes the amount of the heat transfer occurred between the system and surrounding, m denotes the mass of the system, c denotes the specific heat capacity of the system, $\Delta {\text{T}}$ denotes the change in temperature of the system
The units of heat are simply the same as those of energy because heat is the form of energy transfer from one body to another.
As we know that the S.I unit of energy is Joule.
Therefore, the S.I unit of heat is also Joule (J).
Hence, option C is correct.

Note- Basically, there are three different mechanisms through which heat transfer can take place. These are conduction, convection and radiation. The heat transfer between the atoms and molecules in direct contact is termed as conduction, the heat transfers due to the movement of the heated substance itself is termed as convection and the heat transfer due to the electromagnetic waves is termed as radiation.