Question

(a) Explain the structure of candle flame. Also, draw its diagram.

(b) What is calorific value?

(c) What are the characteristics of a good fuel?

Answer 1

(a)


Structure of a Candle flame

It has three main zones, they are-

• The outer zone – complete combustion of the fuel takes place and the colour of the flame is blue and is the hottest part of the flame. It is the non-luminous part of the flame.
• The middle zone -partial combustions of the fuel take place and the colour of the flame is yellow and is a moderately hot part of the flame. It is the luminous part of the flame.
• The inner zone: There are unburnt vapours of the fuel and the colour is black and is the least hot part.

(b) Calorific value is the amount of heat energy present in food or fuel that is determined by the complete combustion of a specified quantity at constant pressure and in normal conditions. It is also called calorific power. The unit of calorific value is kilojoule per kilogram i.e. KJ/Kg.

(c) Characteristics of good fuel:

• Readily available

• Cheap

• Easy transport and store

• Burns at a moderate rate

• Produce a large amount of heat

• Do not leave behind any undesirable substances.

• Does not cause pollution.