Question

Which of the following statements are true? I. Yellow flames are ideal for heating. II. The substances which vaporise during burning give flames. III. Luminous zone contains unburnt carbon particles. IV. The non-luminous zone has highest temperature.
1 point
A) I, II and III
B) I, II and IV
C) II, III and IV
D) I, III and IV
Different methods of extinguishing a fire involve the following : I. Removing the combustible substance. II. Cooling the substance to a temperature below its ignition temperature. III. Cutting off the supply of air. Which of the following statements is correct?
1 point
A) Method I is suitable in case of a building on fire.
B) Method II involves water which works when wood or paper are on fire.
C) Method III involves carbon dioxide gas which is lighter than oxygen and forms a blanket around the air.
D) All of these
Neha took a burning candle and covered it with an empty glass by putting it upside down. She observed that the candle burns for some time before it finally goes off. What is the reason for this?
1 point
A) The candle keeps burning for some time as long as the air present in the glass is available to it
B) The ignition temperature of the candle becomes low due to glass cover hence it goes off.
C) The candle keeps burning as long as the complete wax melts away and then goes off.
D) Oxygen is produced when the candle burns. This oxygen keeps the candle burning for some time
Why is L.P.G, used as domestic fuel, mixed with a strong smelling volatile liquid like mercaptan?
1 point
A) For better combustion
B) For good smell/fragrance
C) For detection of gas leakage
D) For higher calorific value

Answer 1

Answer:

1 option B

. option D

.option D

option b

Answer 2

The true statements are :

D.

1. Yellow flames are ideal for heating.  
2. Luminous zone contains unburnt carbon particles.
3. The non-luminous zone has highest temperature.

D.

1. Method I is suitable in case of a building on fire.
2. Method II involves water which works when wood or paper are on fire.
3. Method III involves carbon dioxide gas which is lighter than oxygen and forms a blanket around the air.

L.P.G, used as domestic fuel, mixed with a strong smelling volatile liquid like mercaptan because

For higher calorific value.