Question

What do you mean by calorific value of a fuel?

Answer 1

Hint:Any substance that helps us to do work, any kind of work is done by energy which is produced by fuel. So fuel can be defined as a substance that gives us energy in heat, nuclear, mechanical or any other form of energy. So fuels are so important to humankind and are like a boon to us.

Complete answer:
As defined above fuel is a boon to mankind but anything that has merits comes with demerits too. Combustion of fuels produces many harmful gases resulting in greenhouse effects.Calorific value is a way to compare which fuel is good to use and produces relatively more energy than other fuel having the same amount. So Calorific value is defined as the amount of heat produced by a given fuel on complete combustion. It is the measure of energy held by a fuel. Unit of calorific value is measured in \[\dfrac{{kJ}}{{kg}}\].

Calorific values of some fuels:

FUEL	CALORIFIC VALUE(\[\dfrac{{kJ}}{{kg}}\])
Cow Dung	\[8000\]
Wood	\[22000\]
Petrol	\[45000\]
LPG	\[55000\]
Fats(\[1\,gram\])	\[9\,kcal\]
Protein(\[1\,gram\])	\[9\,kcal\]

For food calorific value is expressed in kilojoules per \[100\]grams or in kcal.

Note: Higher the value if calorific value better the fuel in terms of combustion. Like calorific value of LPG is more as compared to fuel like petrol, diesel, kerosene so using LPG is a good alternative to these. In food the calorific value shows the energy a food can generate during metabolism. If we consume a limited value of calories needed in metabolism we can stay fit.