Question

The holes are kept below the chimney of an oil lamp:
A. to supply oxygen for burning of the lamp
B. to let the smoke escape
C. to increase the brightness of lamp
D. to maintain convection currents

Answer 1

Hint: It is a structure enclosing a flue which rises above the roof. A fuel burns in the presence of oxygen and this reaction is called combustion. It is a chemical process in which a substance reacts with oxygen of air to give heat and light.

Complete step by step solution:
Generally fuels are in the form of hydrocarbons. When hydrocarbons are burnt in the presence of oxygen, carbon dioxide and water is obtained. The necessary conditions of combustion are:
Presence of combustible substances
Presence of a supporter oxygen
Heating the combustible substances to its ignition temperature
It is an exothermic reaction since it releases thermal energy. For an oil lamp to burn, it needs oxygen. So it needs holes below the chimney for exchange of gases. Since the fuel is burnt to give carbon dioxide, oxygen and carbon dioxide gets exchanged in the presence of holes. The holes thus help in combustion. When holes are left below the chimneys of oil lamps, the rising hot air is replaced with the fresh air and provides oxygen to the lamp. The air flow through the holes stops the chimney from getting too hot. Thus the chimney gets cooled. This is similar to the exposed candle flame.

Hence, the correct option is A.

Note: Kerosene lamp is similar to the oil lamp. But the oil lamp is purified to burn cleanly. Oil lamps produce less pollutants than kerosene lamps. Moreover it is more expensive than the kerosene lamp. The brightness of the oil lamp is less than that of the kerosene lamp.