Question

Name the S.I. unit of heat
(a). Joule (J)
(b). Joule-sec (J-s)
(c). Calorie (C)
(d). Watt (W)

Answer 1

- Hint: Heat is caused due to the change in temperature and it is considered as one of the forms of energy.

Complete step-by-step solution -

Heat is a term which we all use in our daily life. It is a form of energy that gets transferred due to the difference amid the temperatures of two bodies. When two bodies with difference in temperature are in touch with each other, then heat is said to flow from the hottest body to the coldest one. The flow of heat continues till an equilibrium in temperatures is attained.
Since, heat is a form of energy. It is also expressed in terms of the unit of energy. Hence, the unit of heat is Joule (J). We can define joule as the total energy needed to increase the temperature of a given mass by one degree($1^o$).

Additional Information:
Heat is not only measured in joules, but there are other units too. The other units are BTU (British Thermal Unit), and Calorie(cal). BTU is defined as the energy needed to increase the temperature of one pound of water by 1degree Fahrenheit ($1^{o}F$) at sea level, whereas calorie is the amount of energy required to increase the temperature of one gram of water by 1 degree Celsius(($1^{o}C$)).
The relation between these unit is illustrated below:
$$1\text{ joule= 0}\text{.000239006 kcal / 0}\text{.000947817 BTU}$$

Note: The formula of heat is,
$$\text{Q=cm}\mathrm{\Delta }\text{T}$$,
Where Q is added heat, c is specific heat, m is mass, ∆T is change in temperature. Here, specific heat is the amount of heat needed to increase the temperature by 1 degree Celsius($1^{o}C$).