Question

What will be the S.I. unit of heat ?
A. Joule (J)
B. Joule-sec (J – s)
C. Calorie (C)
D. Watt (W)

Answer 1

Hint: Let us write the formula heat because after expanding that we can easily calculate the unit of heat.

Complete step-by-step answer:

As we know that heat is the form of energy which is transferred between two substances at different temperatures. The direction of the flow of energy is from the substance of higher temperature to the substance of lower temperature.

And heat is denoted as Q.

As we know that formula of heat that Q = mC\[\Delta {\text{T}}\]
Where m is the mass of the body. So, its unit will be kilogram (kg).
C is specific heat. And unit of joule per kilogram kelvin \[\left( {J/kg \times k} \right)\].

And \[\Delta {\text{T}}\] is the change in temperature. So, unit of \[\Delta {\text{T}}\] will be the unit of temperature that is kelvin (k)

Now heat of the body is = mC\[\Delta {\text{T}}\] = \[kg \times \dfrac{J}{{kg \times k}} \times k\] = J (Joule)

So, S.I unit of the heat of the body will be Joule (J)

Hence, the correct option will be A.

Note: Whenever we come up with this type of problem where we are asked to find the unit of any quantity. Then we first write the formula to calculate that quantity and then in place of values we put the unit of every quantity. After solving that we will get the required S.I. unit asked for that quantity (here heat).