Q1 of 22 Page 42

A fire alarm usually detects smoke in case of fire. Where should such an alarm be placed in a room?

As we know that the smoke created by the fire is hot air and we know that hot air expands (volume increases) but have same mass as before and it becomes lighter than the ordinary air, so the light air floats up in the sky and rises up, so due to this reason the suitable place for the sensor would be the ceiling.

Warm air rises up cool air sinks down. ALWAYS REMEMBER

More from this chapter

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2

Four schematic diagrams are shown in Figure 8.1 to depict the direction of sea breeze. Which of them gives the correct direction?

 3

Figure 8.2 shows a child blowing air with a straw near the opening of another straw which has its other end in a soft drink bottle. It was observed that the level of the soft drink in the straw rises up as soon as air is blown over its open end. Which one of the following best explains the reason for rise in level of the drink?

 4

Following are precautions one must take in case a storm is accompanied by lightning.

(i) Do not take shelter under a tree.


(ii) Do not take shelter under an umbrella with a metallic end.


(iii) Do not take shelter in open garages, storage sheds, etc.


(iv) Do not take shelter in a bus in the open.


Which one of these is not correct?

 5

Which of the following place is most likely to be affected by a cyclone?