Question

We need mechanical equivalent of heat because :

• A. it converts work into heat
• B. in C.G.S system, heat is not measured in the units of work
• C. in S.I., heat is measured in the units of work
• D. of some reason other than those mentioned above

Answer 1

The correct option is B in C.G.S system, heat is not measured in the units of work

We measure the quantity of heat in the CGS system of units i.e. in calorie(cal) or kilocalorie(Kcal).

But in SI unit use joules (J) to express heat and therefore to make comparison easier we use the conversion factor namely, mechanical equivalent of heat.

$1cal=4.2\times {10}^{7}erg=4.2J$.
This conversion factor to convert heat in CGS to SI system is called mechanical equivalent of heat.