questions and answers for class 8B

Syllabus for second card test are chapters 5 & 6.

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Chapter  6 : Winds ~ .

F : Answer briefly :-

 1) Ferrel's  law  states that all moving bodies get deflected from their straight path to their  right in the northern                       

    hemisphere and to their left in the southern hemisphere due to the rotation of the earth.

2) Two points of  similarities between sea breeze and land breeze and monsoon winds are :

      a) both are caused by differential rate of heating and cooling of land and water.

      b) both reverse their direction periodically and derive  their name accordingly.

3) The two points of contrast are as follows :

   a) Land breeze and sea breeze reverse their their direction in the course in one day . Sea breeze during        

       the  day and land breeze at  night . North east &  South west monsoons do so seasonally in summer and

      winter respectively .

  b) The sea breeze does not bring rainfall as the period during which they blow is not enough for collecting

      moisture from the sea , while the monsoons bring rainfall  as they blow for sufficient length of time .

4) Katabatic winds : On a clear , still , cloudy nights , the mountain tops loose their heat  rapidly due to    

                                radiation . Dense cold air descends the valley slopes under the influence of 

                                gravity . Soon the valley floor gets cold an inversion of temperature takes place .

                                Because of the cold mountain winds which give rise to frost , citrus groves in California                                                                

                                and coffee in Brazil  are grown on hilly slopes than on valley floors . Descending winds

                                are said to be Katabatic winds .

   Anabatic winds : During the day in the hilly areas , warm rises from the valley floors up the slope to        

                               the places of the warm air that has risen from the mountain tops . These ascending winds

                               cause rain when they rise and condense . They are known as Valley winds .

5) While cyclones bring bad whether , anticyclones bring good whether , blue skies , gentle breeze . In an
    anticyclone ,descending air current causes a high pressure centre from which light breeze blow outwards .