Heat - Practice Questions & MCQ

Heat - 

• The form of energy which is exchanged among various bodies or system on account of temperature difference is defined as heat.So, we can say that the driving potential for the heat energy is the temperature differnece.
•  Temperature of a body can be changed by giving heat (temperature rises) or by removing heat (temperature falls) from body.
• The amount of heat (Q) is given to a body depends upon it's mass (m), change in it's temperature and nature of material (C) i.e., $\mathbf{Q}=\mathrm{mC} \boldsymbol{\Delta} \theta$ ;  where C = specific heat of material which depends on the material.
• There are various units of heat like Joule(J), erg, calorie(cal) etc. 
• Heat is a scalar quantity. 
• The calorie (cal) is defined as the amount of heat required to raise the temperature of 1 gram of water by 1^oC. 
• 1 cal = 4.186 J 

There are basically two types of specific heats - 

1. Gram specific heat : It is defined as the amount of heat energy required to raise the temperature of unit mass of a body through 1°C (or K) is called gram specific heat of the material of the body. Actually it depends on the mass of the body which is in Gram.

           If Q heat changes the temperature of mass m by  then specific heat is given as - $c=\frac{Q}{m \Delta \theta}$

          Based on this equation we can calculate the unit and dimension of this - 

SI unit is $=\frac{\text { Joule }}{k g-K}$
Dimension is - $\left[L^2 T^{-2} \boldsymbol{\theta}^{-1}\right]$
2. Molar specific heat : Molar specific heat of a substance is defined as the amount of heat required to raise the temperature of one gram mole of the substance through a unit degree. It is represented by C .

It can be written as -

$$
C=M \frac{Q}{m \Delta \theta}=\frac{1}{\mu} \frac{Q}{\Delta \theta}
$$

Here,
$Q=$ Heat supplied, $M=$ Molecular mass, $m=$ Actual mass of the substance, $\Delta \theta=$
Temperature difference