What is fuel? Explain with examples.

A fuel is a combustible substance that, on burning in air/oxygen, releases heat energy usable for cooking, transport, electricity generation, and industrial work.

A fuel is a substance that produces heat on burning. Common examples include coal and wood (solid), kerosene, petrol, diesel (liquid), and LPG, CNG, biogas (gas). A good fuel has a high calorific value, burns cleanly and safely, and is easy to obtain and use.

Types of fuels with examples

1. Solid fuels:Wood, coal, charcoal, coke
2. Liquid fuels:Kerosene, petrol, diesel
3. Gaseous fuels:LPG (propane–butane), CNG (methane), biogas, natural gas

Everyday uses

• Home: LPG in gas stoves for cooking
• Transport:Petrol, diesel, CNG in vehicles
• Power & industry:Coal, natural gas, diesel for boilers, furnaces, and electricity generation

Calorific value: The heat produced by the complete combustion of 1 kg of a fuel. It is usually expressed in kJ/kg. A higher calorific value means more energy per kilogram.

Characteristics of a “good” fuel

• High calorific value (gives a lot of heat per unit mass)
• Moderate ignition temperature and steady, controllable flame
• Clean burning (little smoke, ash, or harmful gases)
• Readily available, affordable, safe to store and transport
• Leaves minimal residue and does not corrode equipment