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Page 76 - CT&AI_CLasa_7_Part_1
P. 76

    Heat Transfer in

                                     7                                                  Nature

                                               computational thinking quest

                    Tick ( ) the correct option.
                      1.  A new building  is being  fitted  with smoke        makes things worse because the leaked liquid
                         detectors. The safety engineer explains that         will warm the outer tumbler. The shopkeeper
                         smoke  detectors  work by  sensing  particles        says  the arrangement  does  help keep  the
                         suspended  in  air. Hot  smoke  from a  fire         lassi cold.
                         always rises rapidly towards the ceiling before
                         spreading  sideways.  The engineer  must
                         choose between three mounting positions —
                         near the floor, mid-wall, or ceiling.
                         Where should the smoke detector be installed,
                         and what is the scientific principle that makes
                         this the only correct position?
                                                  (Abstract Thinking)

                                (a)   Near the floor, smoke eventually
                                   sinks when it cools.                       Who  is  correct,  and  what role does  the  air
                                                                              gap between the two tumblers play in heat
                                (b)   In the middle of the wall, it detects   transfer?                  (Decomposition)
                                   both rising and falling smoke.
                                                                                    (a)  The shopkeeper is right, the air gap
                                                                                       acts as an insulating layer, slowing
                                (c)   On the ceiling, hot smoke rises by               heat transfer  from the warm
                                   convection and reaches the ceiling                  surroundings into the cold lassi.
                                   first, ensuring earliest detection.
                                                                                    (b)   The customer is right, leaked liquid
                                (d)   Anywhere, smoke fills the room                   conducts heat inward, warming
                                   uniformly within seconds.                           the lassi faster.

                      2.  A  shopkeeper  serves cold  lassi in a  leaky             (c)   It makes no difference, the
                         tumbler. He places the leaky tumbler inside a                 temperature of lassi depends only
                         second tumbler. The lassi now sits in the inner               on the glass material, not air gaps.
                         tumbler, while a thin air gap exists between               (d)   The arrangement helps only if the
                         the  two  tumblers.  A  customer  argues  this                outer tumbler is made of metal.

                     74        Computational Thinking-7 (Science)

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