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Q.5 Give reasons.
(a) Water is not used to control fires involving electrical equipment.
(b) LPG is a better domestic fuel than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.
Answer :

a) Water is a good conductor of electricity.
If added to an electrical fire, the water would just spread the electricity further.
The person dousing the fire might get an electric shock
b) LPG being a cleaner fuel than wood doesn’t release smoke and other pollutants.
Wood, on the other hand, releases a lot of smoke and fumes polluting the atmosphere causing pollution and leading to respiratory diseases.
Hence, LPG is a better domestic fuel than wood.
c) The paper by itself catches fire easily because of its low ignition temperature.
The piece of paper wrapped around an aluminium pipe doesn’t catch fire because aluminium is a good conductor of electricity.
While the paper wrapped around an aluminium pipe results in an increase in ignition temperature. So, there is a transfer of heat from paper to the aluminium pipe. Hence it doesn’t catch fire.